The "stack_trace_filter" file only makes sense if DYNAMIC_FTRACE is
configured in. If it is not, then the user can not filter any functions.

Not only that, the open function causes warnings when DYNAMIC_FTRACE is not
set.

Link: http://lkml.kernel.org/r/20170710110521.600806-1-arnd@arndb.deReported-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>

When doing the following command:

 # echo ":mod:kvm_intel" > /sys/kernel/tracing/stack_trace_filter

it triggered a crash.

This happened with the clean up of probes. It required all callers to the
regex function (doing ftrace filtering) to have ops->private be a pointer to
a trace_array. But for the stack tracer, that is not the case.

Allow for the ops->private to be NULL, and change the function command
callbacks to handle the trace_array pointer being NULL as well.

Fixes: d2afd57a ("tracing/ftrace: Allow instances to have their own function probes")
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>

Tracing uses rcu_irq_enter() as a way to make sure that RCU is watching when
it needs to use rcu_read_lock() and friends. This is because tracing can
happen as RCU is about to enter user space, or about to go idle, and RCU
does not watch for RCU read side critical sections as it makes the
transition.

There is a small location within the RCU infrastructure that rcu_irq_enter()
itself will not work. If tracing were to occur in that section it will break
if it tries to use rcu_irq_enter().

Originally, this happens with the stack_tracer, because it will call
save_stack_trace when it encounters stack usage that is greater than any
stack usage it had encountered previously. There was a case where that
happened in the RCU section where rcu_irq_enter() did not work, and lockdep
complained loudly about it. To fix it, stack tracing added a call to be
disabled and RCU would disable stack tracing during the critical section
that rcu_irq_enter() was inoperable. This solution worked, but there are
other cases that use rcu_irq_enter() and it would be a good idea to let RCU
give a way to let others know that rcu_irq_enter() will not work. For
example, in trace events.

Another helpful aspect of this change is that it also moves the per cpu
variable called in the RCU critical section into a cache locale along with
other RCU per cpu variables used in that same location.

I'm keeping the stack_trace_disable() code, as that still could be used in
the future by places that really need to disable it. And since it's only a
static inline, it wont take up any kernel text if it is not used.

Link: http://lkml.kernel.org/r/20170405093207.404f8deb@gandalf.local.homeAcked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>

In order to eliminate a function call, make "trace_active" into
"disable_stack_tracer" and convert stack_tracer_disable() and friends into
static inline functions.
Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>

There are certain parts of the kernel that cannot let stack tracing
proceed (namely in RCU), because the stack tracer uses RCU, and parts of RCU
internals cannot handle having RCU read side locks taken.

Add stack_tracer_disable() and stack_tracer_enable() functions to let RCU
stop stack tracing on the current CPU when it is in those critical sections.
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>

The updates to the trace_active per cpu variable can be updated with the
__this_cpu_*() functions as it only gets updated on the CPU that the variable
is on.

Thanks to Paul McKenney for suggesting __this_cpu_* instead of this_cpu_*.
Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>

Fix typos and add the following to the scripts/spelling.txt:

  overide||override

While we are here, fix the doubled "address" in the touched line
Documentation/devicetree/bindings/regulator/ti-abb-regulator.txt.

Also, fix the comment block style in the touched hunks in
drivers/media/dvb-frontends/drx39xyj/drx_driver.h.

Link: http://lkml.kernel.org/r/1481573103-11329-21-git-send-email-yamada.masahiro@socionext.comSigned-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We are going to split <linux/sched/task_stack.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/task_stack.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

When enabling stack trace via "echo 1 > /proc/sys/kernel/stack_tracer_enabled",
the below KASAN warning is triggered:

BUG: KASAN: stack-out-of-bounds in check_stack+0x344/0x848 at addr ffffffc0689ebab8
Read of size 8 by task ksoftirqd/4/29
page:ffffffbdc3a27ac0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x0()
page dumped because: kasan: bad access detected
CPU: 4 PID: 29 Comm: ksoftirqd/4 Not tainted 4.5.0-rc1 #129
Hardware name: Freescale Layerscape 2085a RDB Board (DT)
Call trace:
[<ffffffc000091300>] dump_backtrace+0x0/0x3a0
[<ffffffc0000916c4>] show_stack+0x24/0x30
[<ffffffc0009bbd78>] dump_stack+0xd8/0x168
[<ffffffc000420bb0>] kasan_report_error+0x6a0/0x920
[<ffffffc000421688>] kasan_report+0x70/0xb8
[<ffffffc00041f7f0>] __asan_load8+0x60/0x78
[<ffffffc0002e05c4>] check_stack+0x344/0x848
[<ffffffc0002e0c8c>] stack_trace_call+0x1c4/0x370
[<ffffffc0002af558>] ftrace_ops_no_ops+0x2c0/0x590
[<ffffffc00009f25c>] ftrace_graph_call+0x0/0x14
[<ffffffc0000881bc>] fpsimd_thread_switch+0x24/0x1e8
[<ffffffc000089864>] __switch_to+0x34/0x218
[<ffffffc0011e089c>] __schedule+0x3ac/0x15b8
[<ffffffc0011e1f6c>] schedule+0x5c/0x178
[<ffffffc0001632a8>] smpboot_thread_fn+0x350/0x960
[<ffffffc00015b518>] kthread+0x1d8/0x2b0
[<ffffffc0000874d0>] ret_from_fork+0x10/0x40
Memory state around the buggy address:
 ffffffc0689eb980: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 f4 f4 f4
 ffffffc0689eba00: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffc0689eba80: 00 00 f1 f1 f1 f1 00 f4 f4 f4 f3 f3 f3 f3 00 00
                                        ^
 ffffffc0689ebb00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffc0689ebb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

The stacker tracer traverses the whole kernel stack when saving the max stack
trace. It may touch the stack red zones to cause the warning. So, just disable
the instrumentation to silence the warning.

Link: http://lkml.kernel.org/r/1455309960-18930-1-git-send-email-yang.shi@linaro.orgSigned-off-by: NYang Shi <yang.shi@linaro.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When a max stack trace is discovered, the stack dump is saved. In order to
not record the overhead of the stack tracer, the ip of the traced function
is looked for within the dump. The trace is started from the location of
that function. But if for some reason the ip is not found, the entire stack
trace is then truncated. That's not very useful. Instead, print everything
if the ip of the traced function is not found within the trace.

This issue showed up on s390.

Link: http://lkml.kernel.org/r/20160129102241.1b3c9c04@gandalf.local.home

Fixes: 72ac426a ("tracing: Clean up stack tracing and fix fentry updates")
Cc: stable@vger.kernel.org # v4.3+
Reported-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Now that max_stack_lock is a global variable, it requires a naming
convention that is unlikely to collide. Rename it to the same naming
convention that the other stack_trace variables have.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

A stack frame may be used in a different way depending on cpu architecture.
Thus it is not always appropriate to slurp the stack contents, as current
check_stack() does, in order to calcurate a stack index (height) at a given
function call. At least not on arm64.
In addition, there is a possibility that we will mistakenly detect a stale
stack frame which has not been overwritten.

This patch makes check_stack() a weak function so as to later implement
arch-specific version.

Link: http://lkml.kernel.org/r/1446182741-31019-5-git-send-email-takahiro.akashi@linaro.orgSigned-off-by: NAKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The code in stack tracer should not be executed within an NMI as it grabs
spinlocks and stack tracing an NMI gives the possibility of causing a
deadlock. Although this is safe on x86_64, because it does not perform stack
traces when the task struct stack is not in use (interrupts and NMIs), it
may be an issue for NMIs on i386 and other archs that use the same stack as
the NMI.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The stack tracer was triggering the WARN_ON() in module.c:

 static void module_assert_mutex_or_preempt(void)
 {
 #ifdef CONFIG_LOCKDEP
	if (unlikely(!debug_locks))
		return;

	WARN_ON(!rcu_read_lock_sched_held() &&
		!lockdep_is_held(&module_mutex));
 #endif
 }

The reason is that the stack tracer traces all function calls, and some of
those calls happen while exiting or entering user space and idle. Some of
these functions are called after RCU had already stopped watching, as RCU
does not watch userspace or idle CPUs.

If a max stack is hit, then the save_stack_trace() is called, which will
check module addresses and call module_assert_mutex_or_preempt(), and then
trigger the warning. Sad part is, the warning itself will also do a stack
trace and tigger the same warning. That probably should be fixed.

The warning was added by 0be964be "module: Sanitize RCU usage and
locking" but this bug has probably been around longer. But it's unlikely to
cause much harm, but the new warning causes the system to lock up.

Cc: stable@vger.kernel.org # 4.2+
Cc: Peter Zijlstra <peterz@infradead.org>
Cc:"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Akashi Takahiro was porting the stack tracer to arm64 and found some
issues with it. One was that it repeats the top function, due to the
stack frame added by the mcount caller and added by itself. This
was added when fentry came in, and before fentry created its own stack
frame. But x86's fentry now creates its own stack frame, and there's
no need to insert the function again.

This also cleans up the code a bit, where it doesn't need to do something
special for fentry, and doesn't include insertion of a duplicate
entry for the called function being traced.

Link: http://lkml.kernel.org/r/55A646EE.6030402@linaro.orgSome-suggestions-by: NJungseok Lee <jungseoklee85@gmail.com>
Some-suggestions-by: NMark Rutland <mark.rutland@arm.com>
Reported-by: NAKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The seq_printf return value, because it's frequently misused,
will eventually be converted to void.

See: commit 1f33c41c ("seq_file: Rename seq_overflow() to
     seq_has_overflowed() and make public")

Miscellanea:

o Remove unused return value from trace_lookup_stack
Signed-off-by: NJoe Perches <joe@perches.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

tracing_init_dentry() will soon return NULL as a valid pointer for the
top level tracing directroy. NULL can not be used as an error value.
Instead, switch to ERR_PTR() and check the return status with
IS_ERR().
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The creation of tracing files and directories is for the most part
encapsulated in helper functions in trace.c. Other files do not need to
include debugfs.h or fs.h, as they may have needed to in the past.

Remove them from the files that do not need them.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

This facility is used in a few places so let's introduce
a helper function to improve code readability.
Signed-off-by: NAaron Tomlin <atomlin@redhat.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: aneesh.kumar@linux.vnet.ibm.com
Cc: dzickus@redhat.com
Cc: bmr@redhat.com
Cc: jcastillo@redhat.com
Cc: oleg@redhat.com
Cc: riel@redhat.com
Cc: prarit@redhat.com
Cc: jgh@redhat.com
Cc: minchan@kernel.org
Cc: mpe@ellerman.id.au
Cc: tglx@linutronix.de
Cc: hannes@cmpxchg.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1410527779-8133-3-git-send-email-atomlin@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Tasks get their end of stack set to STACK_END_MAGIC with the
aim to catch stack overruns. Currently this feature does not
apply to init_task. This patch removes this restriction.

Note that a similar patch was posted by Prarit Bhargava
some time ago but was never merged:

  http://marc.info/?l=linux-kernel&m=127144305403241&w=2Signed-off-by: NAaron Tomlin <atomlin@redhat.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NMichael Ellerman <mpe@ellerman.id.au>
Cc: aneesh.kumar@linux.vnet.ibm.com
Cc: dzickus@redhat.com
Cc: bmr@redhat.com
Cc: jcastillo@redhat.com
Cc: jgh@redhat.com
Cc: minchan@kernel.org
Cc: tglx@linutronix.de
Cc: hannes@cmpxchg.org
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Daeseok Youn <daeseok.youn@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1410527779-8133-2-git-send-email-atomlin@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

While I played with my own feature(ex, something on the way to reclaim),
the kernel would easily oops. I guessed that the reason had to do with
stack overflow and wanted to prove it.

I discovered the stack tracer which proved to be very useful for me but
the kernel would oops before my user program gather the information via
"watch cat /sys/kernel/debug/tracing/stack_trace" so I couldn't get any
message from that. What I needed was to have the stack tracer emit the
kernel stack usage before it does the oops so I could find what was
hogging the stack.

This patch shows the callstack of max stack usage right before an oops so
we can find a culprit.

So, the result is as follows.

[ 1116.522206] init: lightdm main process (1246) terminated with status 1
[ 1119.922916] init: failsafe-x main process (1272) terminated with status 1
[ 3887.728131] kworker/u24:1 (6637) used greatest stack depth: 256 bytes left
[ 6397.629227] cc1 (9554) used greatest stack depth: 128 bytes left
[ 7174.467392]         Depth    Size   Location    (47 entries)
[ 7174.467392]         -----    ----   --------
[ 7174.467785]   0)     7248     256   get_page_from_freelist+0xa7/0x920
[ 7174.468506]   1)     6992     352   __alloc_pages_nodemask+0x1cd/0xb20
[ 7174.469224]   2)     6640       8   alloc_pages_current+0x10f/0x1f0
[ 7174.469413]   3)     6632     168   new_slab+0x2c5/0x370
[ 7174.469413]   4)     6464       8   __slab_alloc+0x3a9/0x501
[ 7174.469413]   5)     6456      80   __kmalloc+0x1cb/0x200
[ 7174.469413]   6)     6376     376   vring_add_indirect+0x36/0x200
[ 7174.469413]   7)     6000     144   virtqueue_add_sgs+0x2e2/0x320
[ 7174.469413]   8)     5856     288   __virtblk_add_req+0xda/0x1b0
[ 7174.469413]   9)     5568      96   virtio_queue_rq+0xd3/0x1d0
[ 7174.469413]  10)     5472     128   __blk_mq_run_hw_queue+0x1ef/0x440
[ 7174.469413]  11)     5344      16   blk_mq_run_hw_queue+0x35/0x40
[ 7174.469413]  12)     5328      96   blk_mq_insert_requests+0xdb/0x160
[ 7174.469413]  13)     5232     112   blk_mq_flush_plug_list+0x12b/0x140
[ 7174.469413]  14)     5120     112   blk_flush_plug_list+0xc7/0x220
[ 7174.469413]  15)     5008      64   io_schedule_timeout+0x88/0x100
[ 7174.469413]  16)     4944     128   mempool_alloc+0x145/0x170
[ 7174.469413]  17)     4816      96   bio_alloc_bioset+0x10b/0x1d0
[ 7174.469413]  18)     4720      48   get_swap_bio+0x30/0x90
[ 7174.469413]  19)     4672     160   __swap_writepage+0x150/0x230
[ 7174.469413]  20)     4512      32   swap_writepage+0x42/0x90
[ 7174.469413]  21)     4480     320   shrink_page_list+0x676/0xa80
[ 7174.469413]  22)     4160     208   shrink_inactive_list+0x262/0x4e0
[ 7174.469413]  23)     3952     304   shrink_lruvec+0x3e1/0x6a0
[ 7174.469413]  24)     3648      80   shrink_zone+0x3f/0x110
[ 7174.469413]  25)     3568     128   do_try_to_free_pages+0x156/0x4c0
[ 7174.469413]  26)     3440     208   try_to_free_pages+0xf7/0x1e0
[ 7174.469413]  27)     3232     352   __alloc_pages_nodemask+0x783/0xb20
[ 7174.469413]  28)     2880       8   alloc_pages_current+0x10f/0x1f0
[ 7174.469413]  29)     2872     200   __page_cache_alloc+0x13f/0x160
[ 7174.469413]  30)     2672      80   find_or_create_page+0x4c/0xb0
[ 7174.469413]  31)     2592      80   ext4_mb_load_buddy+0x1e9/0x370
[ 7174.469413]  32)     2512     176   ext4_mb_regular_allocator+0x1b7/0x460
[ 7174.469413]  33)     2336     128   ext4_mb_new_blocks+0x458/0x5f0
[ 7174.469413]  34)     2208     256   ext4_ext_map_blocks+0x70b/0x1010
[ 7174.469413]  35)     1952     160   ext4_map_blocks+0x325/0x530
[ 7174.469413]  36)     1792     384   ext4_writepages+0x6d1/0xce0
[ 7174.469413]  37)     1408      16   do_writepages+0x23/0x40
[ 7174.469413]  38)     1392      96   __writeback_single_inode+0x45/0x2e0
[ 7174.469413]  39)     1296     176   writeback_sb_inodes+0x2ad/0x500
[ 7174.469413]  40)     1120      80   __writeback_inodes_wb+0x9e/0xd0
[ 7174.469413]  41)     1040     160   wb_writeback+0x29b/0x350
[ 7174.469413]  42)      880     208   bdi_writeback_workfn+0x11c/0x480
[ 7174.469413]  43)      672     144   process_one_work+0x1d2/0x570
[ 7174.469413]  44)      528     112   worker_thread+0x116/0x370
[ 7174.469413]  45)      416     240   kthread+0xf3/0x110
[ 7174.469413]  46)      176     176   ret_from_fork+0x7c/0xb0
[ 7174.469413] ------------[ cut here ]------------
[ 7174.469413] kernel BUG at kernel/trace/trace_stack.c:174!
[ 7174.469413] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC
[ 7174.469413] Dumping ftrace buffer:
[ 7174.469413]    (ftrace buffer empty)
[ 7174.469413] Modules linked in:
[ 7174.469413] CPU: 0 PID: 440 Comm: kworker/u24:0 Not tainted 3.14.0+ #212
[ 7174.469413] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 7174.469413] Workqueue: writeback bdi_writeback_workfn (flush-253:0)
[ 7174.469413] task: ffff880034170000 ti: ffff880029518000 task.ti: ffff880029518000
[ 7174.469413] RIP: 0010:[<ffffffff8112336e>]  [<ffffffff8112336e>] stack_trace_call+0x2de/0x340
[ 7174.469413] RSP: 0000:ffff880029518290  EFLAGS: 00010046
[ 7174.469413] RAX: 0000000000000030 RBX: 000000000000002f RCX: 0000000000000000
[ 7174.469413] RDX: 0000000000000000 RSI: 000000000000002f RDI: ffffffff810b7159
[ 7174.469413] RBP: ffff8800295182f0 R08: ffffffffffffffff R09: 0000000000000000
[ 7174.469413] R10: 0000000000000001 R11: 0000000000000001 R12: ffffffff82768dfc
[ 7174.469413] R13: 000000000000f2e8 R14: ffff8800295182b8 R15: 00000000000000f8
[ 7174.469413] FS:  0000000000000000(0000) GS:ffff880037c00000(0000) knlGS:0000000000000000
[ 7174.469413] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 7174.469413] CR2: 00002acd0b994000 CR3: 0000000001c0b000 CR4: 00000000000006f0
[ 7174.469413] Stack:
[ 7174.469413]  0000000000000000 ffffffff8114fdb7 0000000000000087 0000000000001c50
[ 7174.469413]  0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 7174.469413]  0000000000000002 ffff880034170000 ffff880034171028 0000000000000000
[ 7174.469413] Call Trace:
[ 7174.469413]  [<ffffffff8114fdb7>] ? get_page_from_freelist+0xa7/0x920
[ 7174.469413]  [<ffffffff816eee3f>] ftrace_call+0x5/0x2f
[ 7174.469413]  [<ffffffff81165065>] ? next_zones_zonelist+0x5/0x70
[ 7174.469413]  [<ffffffff810a23fa>] ? __bfs+0x11a/0x270
[ 7174.469413]  [<ffffffff81165065>] ? next_zones_zonelist+0x5/0x70
[ 7174.469413]  [<ffffffff8114fdb7>] ? get_page_from_freelist+0xa7/0x920
[ 7174.469413]  [<ffffffff8119092f>] ? alloc_pages_current+0x10f/0x1f0
[ 7174.469413]  [<ffffffff811507fd>] __alloc_pages_nodemask+0x1cd/0xb20
[ 7174.469413]  [<ffffffff810a4de6>] ? check_irq_usage+0x96/0xe0
[ 7174.469413]  [<ffffffff816eee3f>] ? ftrace_call+0x5/0x2f
[ 7174.469413]  [<ffffffff8119092f>] alloc_pages_current+0x10f/0x1f0
[ 7174.469413]  [<ffffffff81199cd5>] ? new_slab+0x2c5/0x370
[ 7174.469413]  [<ffffffff81199cd5>] new_slab+0x2c5/0x370
[ 7174.469413]  [<ffffffff816eee3f>] ? ftrace_call+0x5/0x2f
[ 7174.469413]  [<ffffffff816db002>] __slab_alloc+0x3a9/0x501
[ 7174.469413]  [<ffffffff8119af8b>] ? __kmalloc+0x1cb/0x200
[ 7174.469413]  [<ffffffff8141dc46>] ? vring_add_indirect+0x36/0x200
[ 7174.469413]  [<ffffffff8141dc46>] ? vring_add_indirect+0x36/0x200
[ 7174.469413]  [<ffffffff8141dc46>] ? vring_add_indirect+0x36/0x200
[ 7174.469413]  [<ffffffff8119af8b>] __kmalloc+0x1cb/0x200
[ 7174.469413]  [<ffffffff8141de10>] ? vring_add_indirect+0x200/0x200
[ 7174.469413]  [<ffffffff8141dc46>] vring_add_indirect+0x36/0x200
[ 7174.469413]  [<ffffffff8141e402>] virtqueue_add_sgs+0x2e2/0x320
[ 7174.469413]  [<ffffffff8148e35a>] __virtblk_add_req+0xda/0x1b0
[ 7174.469413]  [<ffffffff8148e503>] virtio_queue_rq+0xd3/0x1d0
[ 7174.469413]  [<ffffffff8134aa0f>] __blk_mq_run_hw_queue+0x1ef/0x440
[ 7174.469413]  [<ffffffff8134b0d5>] blk_mq_run_hw_queue+0x35/0x40
[ 7174.469413]  [<ffffffff8134b7bb>] blk_mq_insert_requests+0xdb/0x160
[ 7174.469413]  [<ffffffff8134be5b>] blk_mq_flush_plug_list+0x12b/0x140
[ 7174.469413]  [<ffffffff81342237>] blk_flush_plug_list+0xc7/0x220
[ 7174.469413]  [<ffffffff816e60ef>] ? _raw_spin_unlock_irqrestore+0x3f/0x70
[ 7174.469413]  [<ffffffff816e16e8>] io_schedule_timeout+0x88/0x100
[ 7174.469413]  [<ffffffff816e1665>] ? io_schedule_timeout+0x5/0x100
[ 7174.469413]  [<ffffffff81149415>] mempool_alloc+0x145/0x170
[ 7174.469413]  [<ffffffff8109baf0>] ? __init_waitqueue_head+0x60/0x60
[ 7174.469413]  [<ffffffff811e246b>] bio_alloc_bioset+0x10b/0x1d0
[ 7174.469413]  [<ffffffff81184230>] ? end_swap_bio_read+0xc0/0xc0
[ 7174.469413]  [<ffffffff81184230>] ? end_swap_bio_read+0xc0/0xc0
[ 7174.469413]  [<ffffffff81184110>] get_swap_bio+0x30/0x90
[ 7174.469413]  [<ffffffff81184230>] ? end_swap_bio_read+0xc0/0xc0
[ 7174.469413]  [<ffffffff81184660>] __swap_writepage+0x150/0x230
[ 7174.469413]  [<ffffffff810ab405>] ? do_raw_spin_unlock+0x5/0xa0
[ 7174.469413]  [<ffffffff81184230>] ? end_swap_bio_read+0xc0/0xc0
[ 7174.469413]  [<ffffffff81184515>] ? __swap_writepage+0x5/0x230
[ 7174.469413]  [<ffffffff81184782>] swap_writepage+0x42/0x90
[ 7174.469413]  [<ffffffff8115ae96>] shrink_page_list+0x676/0xa80
[ 7174.469413]  [<ffffffff816eee3f>] ? ftrace_call+0x5/0x2f
[ 7174.469413]  [<ffffffff8115b872>] shrink_inactive_list+0x262/0x4e0
[ 7174.469413]  [<ffffffff8115c1c1>] shrink_lruvec+0x3e1/0x6a0
[ 7174.469413]  [<ffffffff8115c4bf>] shrink_zone+0x3f/0x110
[ 7174.469413]  [<ffffffff816eee3f>] ? ftrace_call+0x5/0x2f
[ 7174.469413]  [<ffffffff8115c9e6>] do_try_to_free_pages+0x156/0x4c0
[ 7174.469413]  [<ffffffff8115cf47>] try_to_free_pages+0xf7/0x1e0
[ 7174.469413]  [<ffffffff81150db3>] __alloc_pages_nodemask+0x783/0xb20
[ 7174.469413]  [<ffffffff8119092f>] alloc_pages_current+0x10f/0x1f0
[ 7174.469413]  [<ffffffff81145c0f>] ? __page_cache_alloc+0x13f/0x160
[ 7174.469413]  [<ffffffff81145c0f>] __page_cache_alloc+0x13f/0x160
[ 7174.469413]  [<ffffffff81146c6c>] find_or_create_page+0x4c/0xb0
[ 7174.469413]  [<ffffffff811463e5>] ? find_get_page+0x5/0x130
[ 7174.469413]  [<ffffffff812837b9>] ext4_mb_load_buddy+0x1e9/0x370
[ 7174.469413]  [<ffffffff81284c07>] ext4_mb_regular_allocator+0x1b7/0x460
[ 7174.469413]  [<ffffffff81281070>] ? ext4_mb_use_preallocated+0x40/0x360
[ 7174.469413]  [<ffffffff816eee3f>] ? ftrace_call+0x5/0x2f
[ 7174.469413]  [<ffffffff81287eb8>] ext4_mb_new_blocks+0x458/0x5f0
[ 7174.469413]  [<ffffffff8127d83b>] ext4_ext_map_blocks+0x70b/0x1010
[ 7174.469413]  [<ffffffff8124e6d5>] ext4_map_blocks+0x325/0x530
[ 7174.469413]  [<ffffffff81253871>] ext4_writepages+0x6d1/0xce0
[ 7174.469413]  [<ffffffff812531a0>] ? ext4_journalled_write_end+0x330/0x330
[ 7174.469413]  [<ffffffff811539b3>] do_writepages+0x23/0x40
[ 7174.469413]  [<ffffffff811d2365>] __writeback_single_inode+0x45/0x2e0
[ 7174.469413]  [<ffffffff811d36ed>] writeback_sb_inodes+0x2ad/0x500
[ 7174.469413]  [<ffffffff811d39de>] __writeback_inodes_wb+0x9e/0xd0
[ 7174.469413]  [<ffffffff811d40bb>] wb_writeback+0x29b/0x350
[ 7174.469413]  [<ffffffff81057c3d>] ? __local_bh_enable_ip+0x6d/0xd0
[ 7174.469413]  [<ffffffff811d6e9c>] bdi_writeback_workfn+0x11c/0x480
[ 7174.469413]  [<ffffffff81070610>] ? process_one_work+0x170/0x570
[ 7174.469413]  [<ffffffff81070672>] process_one_work+0x1d2/0x570
[ 7174.469413]  [<ffffffff81070610>] ? process_one_work+0x170/0x570
[ 7174.469413]  [<ffffffff81071bb6>] worker_thread+0x116/0x370
[ 7174.469413]  [<ffffffff81071aa0>] ? manage_workers.isra.19+0x2e0/0x2e0
[ 7174.469413]  [<ffffffff81078e53>] kthread+0xf3/0x110
[ 7174.469413]  [<ffffffff81078d60>] ? flush_kthread_worker+0x150/0x150
[ 7174.469413]  [<ffffffff816ef0ec>] ret_from_fork+0x7c/0xb0
[ 7174.469413]  [<ffffffff81078d60>] ? flush_kthread_worker+0x150/0x150
[ 7174.469413] Code: c0 49 bc fc 8d 76 82 ff ff ff ff e8 44 5a 5b 00 31 f6 8b 05 95 2b b3 00 48 39 c6 7d 0e 4c 8b 04 f5 20 5f c5 81 49 83 f8 ff 75 11 <0f> 0b 48 63 05 71 5a 64 01 48 29 c3 e9 d0 fd ff ff 48 8d 5e 01
[ 7174.469413] RIP  [<ffffffff8112336e>] stack_trace_call+0x2de/0x340
[ 7174.469413]  RSP <ffff880029518290>
[ 7174.469413] ---[ end trace c97d325b36b718f3 ]---

Link: http://lkml.kernel.org/p/1401683592-1651-1-git-send-email-minchan@kernel.orgSigned-off-by: NMinchan Kim <minchan@kernel.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When using ftrace_ops_list_func, we should skip 4 instead of 3,
to avoid ftrace_call+0x5/0xb appearing in the stack trace:

        Depth    Size   Location    (110 entries)
        -----    ----   --------
  0)     2956       0   update_curr+0xe/0x1e0
  1)     2956      68   ftrace_call+0x5/0xb
  2)     2888      92   enqueue_entity+0x53/0xe80
  3)     2796      80   enqueue_task_fair+0x47/0x7e0
  4)     2716      28   enqueue_task+0x45/0x70
  5)     2688      12   activate_task+0x22/0x30

Add a function using_ftrace_ops_list_func() to test for this while keeping
ftrace_ops_list_func to remain static.

Link: http://lkml.kernel.org/p/1398006644-5935-2-git-send-email-wangjiaxing@insigma.com.cnSigned-off-by: NJiaxing Wang <wangjiaxing@insigma.com.cn>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

It is difficult to detect a stack overrun when it
actually occurs.

We have observed that this type of corruption is often
silent and can go unnoticed. Once the corrupted region
is examined, the outcome is undefined and often
results in sporadic system crashes.

When the stack tracing feature is enabled, let's check
for this condition and take appropriate action.

Note: init_task doesn't get its stack end location
set to STACK_END_MAGIC.

Link: http://lkml.kernel.org/r/1395669837-30209-1-git-send-email-atomlin@redhat.comSigned-off-by: NAaron Tomlin <atomlin@redhat.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Trace event triggers added a lseek that uses the ftrace_filter_lseek()
function. Unfortunately, when function tracing is not configured in
that function is not defined and the kernel fails to build.

This is the second time that function was added to a file ops and
it broke the build due to requiring special config dependencies.

Make a generic tracing_lseek() that all the tracing utilities may
use.

Also, modify the old ftrace_filter_lseek() to return 0 instead of
1 on WRONLY. Not sure why it was a 1 as that does not make sense.

This also changes the old tracing_seek() to modify the file pos
pointer on WRONLY as well.
Reported-by: Nkbuild test robot <fengguang.wu@intel.com>
Tested-by: NTom Zanussi <tom.zanussi@linux.intel.com>
Acked-by: NTom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Check return value and bail out if it's NULL.

Link: http://lkml.kernel.org/r/1365553093-10180-2-git-send-email-namhyung@kernel.org

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: NNamhyung Kim <namhyung@kernel.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Currently set_ftrace_pid and set_graph_function files use seq_lseek
for their fops.  However seq_open() is called only for FMODE_READ in
the fops->open() so that if an user tries to seek one of those file
when she open it for writing, it sees NULL seq_file and then panic.

It can be easily reproduced with following command:

  $ cd /sys/kernel/debug/tracing
  $ echo 1234 | sudo tee -a set_ftrace_pid

In this example, GNU coreutils' tee opens the file with fopen(, "a")
and then the fopen() internally calls lseek().

Link: http://lkml.kernel.org/r/1365663302-2170-1-git-send-email-namhyung@kernel.org

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: NNamhyung Kim <namhyung@kernel.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Currently, the depth reported in the stack tracer stack_trace file
does not match the stack_max_size file. This is because the stack_max_size
includes the overhead of stack tracer itself while the depth does not.

The first time a max is triggered, a calculation is not performed that
figures out the overhead of the stack tracer and subtracts it from
the stack_max_size variable. The overhead is stored and is subtracted
from the reported stack size for comparing for a new max.

Now the stack_max_size corresponds to the reported depth:

 # cat stack_max_size
4640

 # cat stack_trace
        Depth    Size   Location    (48 entries)
        -----    ----   --------
  0)     4640      32   _raw_spin_lock+0x18/0x24
  1)     4608     112   ____cache_alloc+0xb7/0x22d
  2)     4496      80   kmem_cache_alloc+0x63/0x12f
  3)     4416      16   mempool_alloc_slab+0x15/0x17
[...]

While testing against and older gcc on x86 that uses mcount instead
of fentry, I found that pasing in ip + MCOUNT_INSN_SIZE let the
stack trace show one more function deep which was missing before.

Cc: stable@vger.kernel.org
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When gcc 4.6 on x86 is used, the function tracer will use the new
option -mfentry which does a call to "fentry" at every function
instead of "mcount". The significance of this is that fentry is
called as the first operation of the function instead of the mcount
usage of being called after the stack.

This causes the stack tracer to show some bogus results for the size
of the last function traced, as well as showing "ftrace_call" instead
of the function. This is due to the stack frame not being set up
by the function that is about to be traced.

 # cat stack_trace
        Depth    Size   Location    (48 entries)
        -----    ----   --------
  0)     4824     216   ftrace_call+0x5/0x2f
  1)     4608     112   ____cache_alloc+0xb7/0x22d
  2)     4496      80   kmem_cache_alloc+0x63/0x12f

The 216 size for ftrace_call includes both the ftrace_call stack
(which includes the saving of registers it does), as well as the
stack size of the parent.

To fix this, if CC_USING_FENTRY is defined, then the stack_tracer
will reserve the first item in stack_dump_trace[] array when
calling save_stack_trace(), and it will fill it in with the parent ip.
Then the code will look for the parent pointer on the stack and
give the real size of the parent's stack pointer:

 # cat stack_trace
        Depth    Size   Location    (14 entries)
        -----    ----   --------
  0)     2640      48   update_group_power+0x26/0x187
  1)     2592     224   update_sd_lb_stats+0x2a5/0x4ac
  2)     2368     160   find_busiest_group+0x31/0x1f1
  3)     2208     256   load_balance+0xd9/0x662

I'm Cc'ing stable, although it's not urgent, as it only shows bogus
size for item #0, the rest of the trace is legit. It should still be
corrected in previous stable releases.

Cc: stable@vger.kernel.org
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Use the stack of stack_trace_call() instead of check_stack() as
the test pointer for max stack size. It makes it a bit cleaner
and a little more accurate.

Adding stable, as a later fix depends on this patch.

Cc: stable@vger.kernel.org
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

It seems that 'ftrace_enabled' flag should not be used inside the tracer
functions. The ftrace core is using this flag for internal purposes, and
the flag wasn't meant to be used in tracers' runtime checks.

stack tracer is the only tracer that abusing the flag. So stop it from
serving as a bad example.

Also, there is a local 'stack_trace_disabled' flag in the stack tracer,
which is never updated; so it can be removed as well.

Link: http://lkml.kernel.org/r/1342637761-9655-1-git-send-email-anton.vorontsov@linaro.orgSigned-off-by: NAnton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

As more users of the function tracer utility are being added, they do
not always add the necessary recursion protection. To protect from
function recursion due to tracing, if the callback ftrace_ops does not
specifically specify that it protects against recursion (by setting
the FTRACE_OPS_FL_RECURSION_SAFE flag), the list operation will be
called by the mcount trampoline which adds recursion protection.

If the flag is set, then the function will be called directly with no
extra protection.

Note, the list operation is called if more than one function callback
is registered, or if the arch does not support all of the function
tracer features.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Return as the 4th paramater to the function tracer callback the pt_regs.

Later patches that implement regs passing for the architectures will require
having the ftrace_ops set the SAVE_REGS flag, which will tell the arch
to take the time to pass a full set of pt_regs to the ftrace_ops callback
function. If the arch does not support it then it should pass NULL.

If an arch can pass full regs, then it should define:
 ARCH_SUPPORTS_FTRACE_SAVE_REGS to 1

Link: http://lkml.kernel.org/r/20120702201821.019966811@goodmis.orgReviewed-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Currently the function trace callback receives only the ip and parent_ip
of the function that it traced. It would be more powerful to also return
the ops that registered the function as well. This allows the same function
to act differently depending on what ftrace_ops registered it.

Link: http://lkml.kernel.org/r/20120612225424.267254552@goodmis.orgReviewed-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Add stacktrace_filter= to the kernel command line that lets
the user pick specific functions to check the stack on.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The stack_tracer is used to look at every function and check
if the current stack is bigger than the last recorded max stack size.
When a new max is found, then it saves that stack off.

Currently the stack tracer is limited by the global_ops of
the function tracer. As the stack tracer has nothing to do with
the ftrace function tracer, except that it uses it as its internal
engine, the stack tracer should have its own list.

A new file is added to the tracing debugfs directory called:

  stack_trace_filter

that can be used to select which functions you want to check the stack
on.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

This patch replaces the code for getting an unsigned long from a
userspace buffer by a simple call to kstroul_from_user.
This makes it easier to read and less error prone.
Signed-off-by: NPeter Huewe <peterhuewe@gmx.de>
Link: http://lkml.kernel.org/r/1307476707-14762-1-git-send-email-peterhuewe@gmx.deSigned-off-by: NSteven Rostedt <rostedt@goodmis.org>

ftrace_ops that are registered to trace functions can now be
agnostic to each other in respect to what functions they trace.
Each ops has their own hash of the functions they want to trace
and a hash to what they do not want to trace. A empty hash for
the functions they want to trace denotes all functions should
be traced that are not in the notrace hash.

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

All file_operations should get a .llseek operation so we can make
nonseekable_open the default for future file operations without a
.llseek pointer.

The three cases that we can automatically detect are no_llseek, seq_lseek
and default_llseek. For cases where we can we can automatically prove that
the file offset is always ignored, we use noop_llseek, which maintains
the current behavior of not returning an error from a seek.

New drivers should normally not use noop_llseek but instead use no_llseek
and call nonseekable_open at open time.  Existing drivers can be converted
to do the same when the maintainer knows for certain that no user code
relies on calling seek on the device file.

The generated code is often incorrectly indented and right now contains
comments that clarify for each added line why a specific variant was
chosen. In the version that gets submitted upstream, the comments will
be gone and I will manually fix the indentation, because there does not
seem to be a way to do that using coccinelle.

Some amount of new code is currently sitting in linux-next that should get
the same modifications, which I will do at the end of the merge window.

Many thanks to Julia Lawall for helping me learn to write a semantic
patch that does all this.

===== begin semantic patch =====
// This adds an llseek= method to all file operations,
// as a preparation for making no_llseek the default.
//
// The rules are
// - use no_llseek explicitly if we do nonseekable_open
// - use seq_lseek for sequential files
// - use default_llseek if we know we access f_pos
// - use noop_llseek if we know we don't access f_pos,
//   but we still want to allow users to call lseek
//
@ open1 exists @
identifier nested_open;
@@
nested_open(...)
{
<+...
nonseekable_open(...)
...+>
}

@ open exists@
identifier open_f;
identifier i, f;
identifier open1.nested_open;
@@
int open_f(struct inode *i, struct file *f)
{
<+...
(
nonseekable_open(...)
|
nested_open(...)
)
...+>
}

@ read disable optional_qualifier exists @
identifier read_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
expression E;
identifier func;
@@
ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
{
<+...
(
   *off = E
|
   *off += E
|
   func(..., off, ...)
|
   E = *off
)
...+>
}

@ read_no_fpos disable optional_qualifier exists @
identifier read_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
@@
ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
{
... when != off
}

@ write @
identifier write_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
expression E;
identifier func;
@@
ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
{
<+...
(
  *off = E
|
  *off += E
|
  func(..., off, ...)
|
  E = *off
)
...+>
}

@ write_no_fpos @
identifier write_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
@@
ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
{
... when != off
}

@ fops0 @
identifier fops;
@@
struct file_operations fops = {
 ...
};

@ has_llseek depends on fops0 @
identifier fops0.fops;
identifier llseek_f;
@@
struct file_operations fops = {
...
 .llseek = llseek_f,
...
};

@ has_read depends on fops0 @
identifier fops0.fops;
identifier read_f;
@@
struct file_operations fops = {
...
 .read = read_f,
...
};

@ has_write depends on fops0 @
identifier fops0.fops;
identifier write_f;
@@
struct file_operations fops = {
...
 .write = write_f,
...
};

@ has_open depends on fops0 @
identifier fops0.fops;
identifier open_f;
@@
struct file_operations fops = {
...
 .open = open_f,
...
};

// use no_llseek if we call nonseekable_open
////////////////////////////////////////////
@ nonseekable1 depends on !has_llseek && has_open @
identifier fops0.fops;
identifier nso ~= "nonseekable_open";
@@
struct file_operations fops = {
...  .open = nso, ...
+.llseek = no_llseek, /* nonseekable */
};

@ nonseekable2 depends on !has_llseek @
identifier fops0.fops;
identifier open.open_f;
@@
struct file_operations fops = {
...  .open = open_f, ...
+.llseek = no_llseek, /* open uses nonseekable */
};

// use seq_lseek for sequential files
/////////////////////////////////////
@ seq depends on !has_llseek @
identifier fops0.fops;
identifier sr ~= "seq_read";
@@
struct file_operations fops = {
...  .read = sr, ...
+.llseek = seq_lseek, /* we have seq_read */
};

// use default_llseek if there is a readdir
///////////////////////////////////////////
@ fops1 depends on !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier readdir_e;
@@
// any other fop is used that changes pos
struct file_operations fops = {
... .readdir = readdir_e, ...
+.llseek = default_llseek, /* readdir is present */
};

// use default_llseek if at least one of read/write touches f_pos
/////////////////////////////////////////////////////////////////
@ fops2 depends on !fops1 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read.read_f;
@@
// read fops use offset
struct file_operations fops = {
... .read = read_f, ...
+.llseek = default_llseek, /* read accesses f_pos */
};

@ fops3 depends on !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier write.write_f;
@@
// write fops use offset
struct file_operations fops = {
... .write = write_f, ...
+	.llseek = default_llseek, /* write accesses f_pos */
};

// Use noop_llseek if neither read nor write accesses f_pos
///////////////////////////////////////////////////////////

@ fops4 depends on !fops1 && !fops2 && !fops3 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read_no_fpos.read_f;
identifier write_no_fpos.write_f;
@@
// write fops use offset
struct file_operations fops = {
...
 .write = write_f,
 .read = read_f,
...
+.llseek = noop_llseek, /* read and write both use no f_pos */
};

@ depends on has_write && !has_read && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier write_no_fpos.write_f;
@@
struct file_operations fops = {
... .write = write_f, ...
+.llseek = noop_llseek, /* write uses no f_pos */
};

@ depends on has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read_no_fpos.read_f;
@@
struct file_operations fops = {
... .read = read_f, ...
+.llseek = noop_llseek, /* read uses no f_pos */
};

@ depends on !has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
@@
struct file_operations fops = {
...
+.llseek = noop_llseek, /* no read or write fn */
};
===== End semantic patch =====
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Cc: Julia Lawall <julia@diku.dk>
Cc: Christoph Hellwig <hch@infradead.org>

save_stack_trace() stores the instruction pointer, not the
function descriptor. On ppc64 the trace stack code currently
dereferences the instruction pointer and shows 8 bytes of
instructions in our backtraces:

 # cat /sys/kernel/debug/tracing/stack_trace
        Depth    Size   Location    (26 entries)
        -----    ----   --------
  0)     5424     112   0x6000000048000004
  1)     5312     160   0x60000000ebad01b0
  2)     5152     160   0x2c23000041c20030
  3)     4992     240   0x600000007c781b79
  4)     4752     160   0xe84100284800000c
  5)     4592     192   0x600000002fa30000
  6)     4400     256   0x7f1800347b7407e0
  7)     4144     208   0xe89f0108f87f0070
  8)     3936     272   0xe84100282fa30000

Since we aren't dealing with function descriptors, use %pS
instead of %pF to fix it:

 # cat /sys/kernel/debug/tracing/stack_trace
        Depth    Size   Location    (26 entries)
        -----    ----   --------
  0)     5424     112   ftrace_call+0x4/0x8
  1)     5312     160   .current_io_context+0x28/0x74
  2)     5152     160   .get_io_context+0x48/0xa0
  3)     4992     240   .cfq_set_request+0x94/0x4c4
  4)     4752     160   .elv_set_request+0x60/0x84
  5)     4592     192   .get_request+0x2d4/0x468
  6)     4400     256   .get_request_wait+0x7c/0x258
  7)     4144     208   .__make_request+0x49c/0x610
  8)     3936     272   .generic_make_request+0x390/0x434
Signed-off-by: NAnton Blanchard <anton@samba.org>
Cc: rostedt@goodmis.org
Cc: fweisbec@gmail.com
LKML-Reference: <20100825013238.GE28360@kryten>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The ftrace_preempt_disable/enable functions were to address a
recursive race caused by the function tracer. The function tracer
traces all functions which makes it easily susceptible to recursion.
One area was preempt_enable(). This would call the scheduler and
the schedulre would call the function tracer and loop.
(So was it thought).

The ftrace_preempt_disable/enable was made to protect against recursion
inside the scheduler by storing the NEED_RESCHED flag. If it was
set before the ftrace_preempt_disable() it would not call schedule
on ftrace_preempt_enable(), thinking that if it was set before then
it would have already scheduled unless it was already in the scheduler.

This worked fine except in the case of SMP, where another task would set
the NEED_RESCHED flag for a task on another CPU, and then kick off an
IPI to trigger it. This could cause the NEED_RESCHED to be saved at
ftrace_preempt_disable() but the IPI to arrive in the the preempt
disabled section. The ftrace_preempt_enable() would not call the scheduler
because the flag was already set before entring the section.

This bug would cause a missed preemption check and cause lower latencies.

Investigating further, I found that the recusion caused by the function
tracer was not due to schedule(), but due to preempt_schedule(). Now
that preempt_schedule is completely annotated with notrace, the recusion
no longer is an issue.
Reported-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>