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>

Robustify refcounting.
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160126045947.GA40151@ast-mbp.thefacebook.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

While cleaning the stacktrace code I unintentially changed the skip depth of
trace_buffer_unlock_commit_regs() from 0 to 6. kprobes uses this function,
and with skipping 6 call backs, it can easily produce no stack.

Here's how I tested it:

 # echo 'p:ext4_sync_fs ext4_sync_fs ' > /sys/kernel/debug/tracing/kprobe_events
 # echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable
 # cat /sys/kernel/debug/trace
            sync-2394  [005]   502.457060: ext4_sync_fs: (ffffffff81317650)
            sync-2394  [005]   502.457063: kernel_stack:         <stack trace>
            sync-2394  [005]   502.457086: ext4_sync_fs: (ffffffff81317650)
            sync-2394  [005]   502.457087: kernel_stack:         <stack trace>
            sync-2394  [005]   502.457091: ext4_sync_fs: (ffffffff81317650)

After putting back the skip stack to zero, we have:

            sync-2270  [000]   748.052693: ext4_sync_fs: (ffffffff81317650)
            sync-2270  [000]   748.052695: kernel_stack:         <stack trace>
 => iterate_supers (ffffffff8126412e)
 => sys_sync (ffffffff8129c4b6)
 => entry_SYSCALL_64_fastpath (ffffffff8181f0b2)
            sync-2270  [000]   748.053017: ext4_sync_fs: (ffffffff81317650)
            sync-2270  [000]   748.053019: kernel_stack:         <stack trace>
 => iterate_supers (ffffffff8126412e)
 => sys_sync (ffffffff8129c4b6)
 => entry_SYSCALL_64_fastpath (ffffffff8181f0b2)
            sync-2270  [000]   748.053381: ext4_sync_fs: (ffffffff81317650)
            sync-2270  [000]   748.053383: kernel_stack:         <stack trace>
 => iterate_supers (ffffffff8126412e)
 => sys_sync (ffffffff8129c4b6)
 => entry_SYSCALL_64_fastpath (ffffffff8181f0b2)

Cc: stable@vger.kernel.org # v4.4+
Fixes: 73dddbb5 "tracing: Only create stacktrace option when STACKTRACE is configured"
Reported-by: NBrendan Gregg <brendan.d.gregg@gmail.com>
Tested-by: NBrendan Gregg <brendan.d.gregg@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

We hit ftrace_bug report when booting Android on a 64bit ATOM SOC chip.
Basically, there is a race between insmod and ftrace_run_update_code.

After load_module=>ftrace_module_init, another thread jumps in to call
ftrace_run_update_code=>ftrace_arch_code_modify_prepare
                        =>set_all_modules_text_rw, to change all modules
as RW. Since the new module is at MODULE_STATE_UNFORMED, the text attribute
is not changed. Then, the 2nd thread goes ahead to change codes.
However, load_module continues to call complete_formation=>set_section_ro_nx,
then 2nd thread would fail when probing the module's TEXT.

The patch fixes it by using notifier to delay the enabling of ftrace
records to the time when module is at state MODULE_STATE_COMING.

Link: http://lkml.kernel.org/r/567CE628.3000609@intel.comSigned-off-by: NQiu Peiyang <peiyangx.qiu@intel.com>
Signed-off-by: NZhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Qiu Peiyang pointed out that there's a race when enabling function tracing
and loading a module. In order to make the modifications of converting nops
in the prologue of functions into callbacks, the text needs to be converted
from read-only to read-write. When enabling function tracing, the text
permission is updated, the functions are modified, and then they are put
back.

When loading a module, the updates to convert function calls to mcount is
done before the module text is set to read-only. But after it is done, the
module text is visible by the function tracer. Thus we have the following
race:

	CPU 0			CPU 1
	-----			-----
   start function tracing
   set text to read-write
			     load_module
			     add functions to ftrace
			     set module text read-only

   update all functions to callbacks
   modify module functions too
   < Can't it's read-only >

When this happens, ftrace detects the issue and disables itself till the
next reboot.

To fix this, a new DISABLED flag is added for ftrace records, which all
module functions get when they are added. Then later, after the module code
is all set, the records will have the DISABLED flag cleared, and they will
be enabled if any callback wants all functions to be traced.

Note, this doesn't add the delay to later. It simply changes the
ftrace_module_init() to do both the setting of DISABLED records, and then
immediately calls the enable code. This helps with testing this new code as
it has the same behavior as previously. Another change will come after this
to have the ftrace_module_enable() called after the text is set to
read-only.

Cc: Qiu Peiyang <peiyangx.qiu@intel.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When we do cat /sys/kernel/debug/tracing/printk_formats, we hit kernel
panic at t_show.

general protection fault: 0000 [#1] PREEMPT SMP
CPU: 0 PID: 2957 Comm: sh Tainted: G W  O 3.14.55-x86_64-01062-gd4acdc7 #2
RIP: 0010:[<ffffffff811375b2>]
 [<ffffffff811375b2>] t_show+0x22/0xe0
RSP: 0000:ffff88002b4ebe80  EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000004
RDX: 0000000000000004 RSI: ffffffff81fd26a6 RDI: ffff880032f9f7b1
RBP: ffff88002b4ebe98 R08: 0000000000001000 R09: 000000000000ffec
R10: 0000000000000000 R11: 000000000000000f R12: ffff880004d9b6c0
R13: 7365725f6d706400 R14: ffff880004d9b6c0 R15: ffffffff82020570
FS:  0000000000000000(0000) GS:ffff88003aa00000(0063) knlGS:00000000f776bc40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f6c02ff0 CR3: 000000002c2b3000 CR4: 00000000001007f0
Call Trace:
 [<ffffffff811dc076>] seq_read+0x2f6/0x3e0
 [<ffffffff811b749b>] vfs_read+0x9b/0x160
 [<ffffffff811b7f69>] SyS_read+0x49/0xb0
 [<ffffffff81a3a4b9>] ia32_do_call+0x13/0x13
 ---[ end trace 5bd9eb630614861e ]---
Kernel panic - not syncing: Fatal exception

When the first time find_next calls find_next_mod_format, it should
iterate the trace_bprintk_fmt_list to find the first print format of
the module. However in current code, start_index is smaller than *pos
at first, and code will not iterate the list. Latter container_of will
get the wrong address with former v, which will cause mod_fmt be a
meaningless object and so is the returned mod_fmt->fmt.

This patch will fix it by correcting the start_index. After fixed,
when the first time calls find_next_mod_format, start_index will be
equal to *pos, and code will iterate the trace_bprintk_fmt_list to
get the right module printk format, so is the returned mod_fmt->fmt.

Link: http://lkml.kernel.org/r/5684B900.9000309@intel.com

Cc: stable@vger.kernel.org # 3.12+
Fixes: 102c9323 "tracing: Add __tracepoint_string() to export string pointers"
Signed-off-by: NQiu Peiyang <peiyangx.qiu@intel.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

A _lot_ of ->write() instances were open-coding it; some are
converted to memdup_user_nul(), a lot more remain...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

The file tracing_enable is obsolete and does not exist anymore. Replace
the comment that references it with the proper tracing_on file.

Link: http://lkml.kernel.org/r/1450787141-45544-1-git-send-email-chuhu@redhat.comSigned-off-by: NChuyu Hu <chuhu@redhat.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The start and end variables were only used when ftrace_module_init() was
split up into multiple functions. No need to keep them around after the
merger.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Simple cleanup. No need for two functions here.
The whole work can simply be done inside 'ftrace_module_init'.

Link: http://lkml.kernel.org/r/1449067197-5718-1-git-send-email-abelvesa@linux.comSigned-off-by: NAbel Vesa <abelvesa@linux.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

This bpf_verifier_ops structure is never modified, like the other
bpf_verifier_ops structures, so declare it as const.

Done with the help of Coccinelle.

Link: http://lkml.kernel.org/r/1449855359-13724-1-git-send-email-Julia.Lawall@lip6.frSigned-off-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Jiri Olsa noted that the change to replace the control_ops did not update
the trampoline for when running perf on a single CPU and with CONFIG_PREEMPT
disabled (where dynamic ops, like perf, can use trampolines directly). The
result was that perf function could be called when RCU is not watching as
well as not handle the ftrace_local_disable().

Modify the ftrace_ops_get_func() to also check the RCU and PER_CPU ops flags
and use the recursive function if they are set. The recursive function is
modified to check those flags and execute the appropriate checks if they are
set.

Link: http://lkml.kernel.org/r/20151201134213.GA14155@krava.brq.redhat.comReported-by: NJiri Olsa <jolsa@redhat.com>
Patch-fixed-up-by: NJiri Olsa <jolsa@redhat.com>
Tested-by: NJiri Olsa <jolsa@kernel.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Currently perf has its own list function within the ftrace infrastructure
that seems to be used only to allow for it to have per-cpu disabling as well
as a check to make sure that it's not called while RCU is not watching. It
uses something called the "control_ops" which is used to iterate over ops
under it with the control_list_func().

The problem is that this control_ops and control_list_func unnecessarily
complicates the code. By replacing FTRACE_OPS_FL_CONTROL with two new flags
(FTRACE_OPS_FL_RCU and FTRACE_OPS_FL_PER_CPU) we can remove all the code
that is special with the control ops and add the needed checks within the
generic ftrace_list_func().
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When showing all tramps registered to a ftrace record in the file
enabled_functions, it exits the loop with ops == NULL. But then it is
suppose to show the function on the ops->trampoline and
add_trampoline_func() is called with the given ops. But because ops is now
NULL (to exit the loop), it always shows the static trampoline instead of
the one that is really registered to the record.

The call to add_trampoline_func() that shows the trampoline for the given
ops needs to be called at every iteration.

Fixes: 39daa7b9 "ftrace: Show all tramps registered to a record on ftrace_bug()"
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

s/ARCH_SUPPORT_FTARCE_OPS/ARCH_SUPPORTS_FTRACE_OPS/

Link: http://lkml.kernel.org/r/1448879016-8659-1-git-send-email-huawei.libin@huawei.comSigned-off-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The set_event_pid filter relies on attaching to the sched_switch and
sched_wakeup tracepoints to see if it should filter the tracing on schedule
tracepoints. By adding the callbacks to sched_wakeup, pids in the
set_event_pid file will trace the wakeups of those tasks with those pids.

But sched_wakeup_new and sched_waking were missed. These two should also be
traced. Luckily, these tracepoints share the same class as sched_wakeup
which means they can use the same pre and post callbacks as sched_wakeup
does.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When an anomaly is detected in the function call modification code,
ftrace_bug() is called to disable function tracing as well as give any
information that may help debug the problem. Currently, only the first found
trampoline that is attached to the failed record is reported. Instead, show
all trampolines that are hooked to it.

Also, not only show the ops pointer but also report the function it calls.

While at it, add this info to the enabled_functions debug file too.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When an anomaly is found while modifying function code, ftrace_bug() is
called which disables the function tracing infrastructure and reports
information about what failed. If the code that is to be replaced does not
match what is expected, then actual code is shown. Currently there is no
arch generic way to show what was expected.

Add a new variable pointer calld ftrace_expected that the arch code can set
to point to what it expected so that ftrace_bug() can report the actual text
as well as the text that was expected to be there.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The ftrace function hook utility has several internal checks to make sure
that whatever it modifies is exactly what it expects to be modifying. This
is essential as modifying running code can be extremely dangerous to the
system.

When an anomaly is detected, ftrace_bug() is called which sends a splat to
the console and disables function tracing. There's some extra information
that is printed to help diagnose the issue.

One thing that is missing though is output of what ftrace was doing at the
time of the crash. Was it updating a call site or perhaps converting a call
site to a nop? A new global enum variable is created to state what ftrace
was doing at the time of the anomaly, and this is reported in ftrace_bug().
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When a trigger is enabled, the cond flag should be set beforehand,
otherwise a trigger that's expecting to process a trace record
(e.g. one with post_trigger set) could be invoked without one.

Likewise a trigger's cond flag should be reset after it's disabled,
not before.

Link: http://lkml.kernel.org/r/a420b52a67b1c2d3cab017914362d153255acb99.1448303214.git.tom.zanussi@linux.intel.comSigned-off-by: NTom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: NDaniel Wagner <daniel.wagner@bmw-carit.de>
Reviewed-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: NNamhyung Kim <namhyung@kernel.org>
Tested-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

When crossing over to a new page, commit the current work. This will allow
readers to get data with less latency, and also simplifies the work to get
timestamps working for interrupted events.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The first commit of a buffer page updates the timestamp of that page. No
need to have the update to the next page add the timestamp too. It will only
be replaced by the first commit on that page anyway.

Only update to a page if it contains an event.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

As cpu_buffer->tail_page may be modified by interrupts at almost any time,
the flow of logic is very important. Do not let gcc get smart with
re-reading cpu_buffer->tail_page by adding READ_ONCE() around most of its
accesses.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Commit fcc742ea "ring-buffer: Add event descriptor to simplify passing
data" added a descriptor that holds various data instead of passing around
several variables through parameters. The problem was that one of the
parameters was modified in a function and the code was designed not to have
an effect on that modified  parameter. Now that the parameter is a
descriptor and any modifications to it are non-volatile, the size of the
data could be unnecessarily expanded.

Remove the extra space added if a timestamp was added and the event went
across the page.

Cc: stable@vger.kernel.org # 4.3+
Fixes: fcc742ea "ring-buffer: Add event descriptor to simplify passing data"
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Do not update the read stamp after swapping out the reader page from the
write buffer. If the reader page is swapped out of the buffer before an
event is written to it, then the read_stamp may get an out of date
timestamp, as the page timestamp is updated on the first commit to that
page.

rb_get_reader_page() only returns a page if it has an event on it, otherwise
it will return NULL. At that point, check if the page being returned has
events and has not been read yet. Then at that point update the read_stamp
to match the time stamp of the reader page.

Cc: stable@vger.kernel.org # 2.6.30+
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

There were still a number of references to my old Red Hat email
address in the kernel source. Remove these while keeping the
Red Hat copyright notices intact.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Arnd Bergmann reported:

  In my ARM randconfig tests, I'm getting a build error for
  newly added code in bpf_perf_event_read and bpf_perf_event_output
  whenever CONFIG_PERF_EVENTS is disabled:

  kernel/trace/bpf_trace.c: In function 'bpf_perf_event_read':
  kernel/trace/bpf_trace.c:203:11: error: 'struct perf_event' has no member named 'oncpu'
  if (event->oncpu != smp_processor_id() ||
           ^
  kernel/trace/bpf_trace.c:204:11: error: 'struct perf_event' has no member named 'pmu'
        event->pmu->count)

  This can happen when UPROBE_EVENT is enabled but KPROBE_EVENT
  is disabled. I'm not sure if that is a configuration we care
  about, otherwise we could prevent this case from occuring by
  adding Kconfig dependencies.

Looking at this further, it's really that UPROBE_EVENT enables PERF_EVENTS.
By just having BPF_EVENTS depend on PERF_EVENTS, then all is fine.

Link: http://lkml.kernel.org/r/4525348.Aq9YoXkChv@wuerfelReported-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

tracing_max_lat_fops is used only when TRACER_MAX_TRACE enabled, so also
swith the related code. The related warning with defconfig under x86_64:

    CC      kernel/trace/trace.o
  kernel/trace/trace.c:5466:37: warning: ‘tracing_max_lat_fops’ defined but not used [-Wunused-const-variable]
   static const struct file_operations tracing_max_lat_fops = {
Signed-off-by: NChen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Since the ring buffer is lockless, there is no need to disable ftrace on
CPU. And no one doing so: after commit 68179686 ("tracing: Remove
ftrace_disable/enable_cpu()") ftrace_cpu_disabled stays the same after
initialization, nothing changes it.
ftrace_cpu_disabled shouldn't be used by any external module since it
disables only function and graph_function tracers but not any other
tracer.

Link: http://lkml.kernel.org/r/1446836846-22239-1-git-send-email-0x7f454c46@gmail.comSigned-off-by: NDmitry Safonov <0x7f454c46@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Currently tracing_init_dentry() returns -ENODEV when debugfs is not
configured in, which causes tracefs not populated with tracing files and
directories, so we will get an empty directory even after we manually
mount tracefs.

We can make tracing_init_dentry() return NULL if debugfs is not
configured in and can manually mount tracefs. But return -ENODEV
if debugfs is configured in but not initialized or failed to create
automount point as that would break backward compatibility with older
tools.

Link: http://lkml.kernel.org/r/1446797056-11683-1-git-send-email-hello.wjx@gmail.comSigned-off-by: NJiaxing Wang <hello.wjx@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Both early_enable_events() and apply_trace_boot_options() parse a boot
string that may get parsed later on. They both use strsep() which converts a
comma into a nul character. To still allow the boot string to be parsed
again the same way, the nul character gets converted back to a comma after
the token is processed.

The problem is that these two functions check for an empty parameter (two
commas in a row ",,"), and continue the loop if the parameter is empty, but
fails to place the comma back. In this case, the second parsing will end at
this blank field, and not process fields afterward.

In most cases, users should not have an empty field, but if its going to be
checked, the code might as well be correct.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Currently, the trace_options parameter is only applied in
tracer_alloc_buffers() when global_trace.current_trace is nop_trace,
so a tracer specific option will not be applied even when the specific
tracer is also enabled from kernel command line. For example, the
'func_stack_trace' option can't be enabled with the following kernel
parameter:

  ftrace=function ftrace_filter=kfree trace_options=func_stack_trace

We can enable tracer specific options by simply apply the options again
if the specific tracer is also supplied from command line and started
in register_tracer().

To make trace_boot_options_buf can be parsed again, a comma and a space
is put back if they were replaced by strsep and strstrip respectively.

Also make register_tracer() be __init to access the __init data, and
in fact register_tracer is only called from __init code.

Link: http://lkml.kernel.org/r/1446599669-9294-1-git-send-email-hello.wjx@gmail.comSigned-off-by: NJiaxing Wang <hello.wjx@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

wake_up_process() has a memory barrier before doing anything, thus adding a
memory barrier before calling it is redundant.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

We don't init iter->started when dumping the ftrace buffer, and there's no
real need to do so - so allow skipping that check if the iter doesn't have
an initialized ->started cpumask.

Link: http://lkml.kernel.org/r/1441385156-27279-1-git-send-email-sasha.levin@oracle.comSigned-off-by: NSasha Levin <sasha.levin@oracle.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

The commit b44754d8 ("ring_buffer: Allow to exit the ring
buffer benchmark immediately") added a hack into ring_buffer_producer()
that set @kill_test when kthread_should_stop() returned true. It improved
the situation a lot. It stopped the kthread in most cases because
the producer spent most of the time in the patched while cycle.

But there are still few possible races when kthread_should_stop()
is set outside of the cycle. Then we do not set @kill_test and
some other checks pass.

This patch adds a better fix. It renames @test_kill/TEST_KILL() into
a better descriptive @test_error/TEST_ERROR(). Also it introduces
break_test() function that checks for both @test_error and
kthread_should_stop().

The new function is used in the producer when the check for @test_error
is not enough. It is not used in the consumer because its state
is manipulated by the producer via the "reader_finish" variable.

Also we add a missing check into ring_buffer_producer_thread()
between setting TASK_INTERRUPTIBLE and calling schedule_timeout().
Otherwise, we might miss a wakeup from kthread_stop().

Link: http://lkml.kernel.org/r/1441629518-32712-3-git-send-email-pmladek@suse.comSigned-off-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

It seems that complete(&read_done) might be called too early
in some situations.

1st scenario:
-------------

CPU0					CPU1

ring_buffer_producer_thread()
  wake_up_process(consumer);
  wait_for_completion(&read_start);

					ring_buffer_consumer_thread()
					  complete(&read_start);

  ring_buffer_producer()
    # producing data in
    # the do-while cycle

					  ring_buffer_consumer();
					    # reading data
					    # got error
					    # set kill_test = 1;
					    set_current_state(
						TASK_INTERRUPTIBLE);
					    if (reader_finish)  # false
					    schedule();

    # producer still in the middle of
    # do-while cycle
    if (consumer && !(cnt % wakeup_interval))
      wake_up_process(consumer);

					    # spurious wakeup
					    while (!reader_finish &&
						   !kill_test)
					    # leaving because
					    # kill_test == 1
					    reader_finish = 0;
					    complete(&read_done);

1st BANG: We might access uninitialized "read_done" if this is the
	  the first round.

    # producer finally leaving
    # the do-while cycle because kill_test == 1;

    if (consumer) {
      reader_finish = 1;
      wake_up_process(consumer);
      wait_for_completion(&read_done);

2nd BANG: This will never complete because consumer already did
	  the completion.

2nd scenario:
-------------

CPU0					CPU1

ring_buffer_producer_thread()
  wake_up_process(consumer);
  wait_for_completion(&read_start);

					ring_buffer_consumer_thread()
					  complete(&read_start);

  ring_buffer_producer()
    # CPU3 removes the module	  <--- difference from
    # and stops producer          <--- the 1st scenario
    if (kthread_should_stop())
      kill_test = 1;

					  ring_buffer_consumer();
					    while (!reader_finish &&
						   !kill_test)
					    # kill_test == 1 => we never go
					    # into the top level while()
					    reader_finish = 0;
					    complete(&read_done);

    # producer still in the middle of
    # do-while cycle
    if (consumer && !(cnt % wakeup_interval))
      wake_up_process(consumer);

					    # spurious wakeup
					    while (!reader_finish &&
						   !kill_test)
					    # leaving because kill_test == 1
					    reader_finish = 0;
					    complete(&read_done);

BANG: We are in the same "bang" situations as in the 1st scenario.

Root of the problem:
--------------------

ring_buffer_consumer() must complete "read_done" only when "reader_finish"
variable is set. It must not be skipped due to other conditions.

Note that we still must keep the check for "reader_finish" in a loop
because there might be spurious wakeups as described in the
above scenarios.

Solution:
----------

The top level cycle in ring_buffer_consumer() will finish only when
"reader_finish" is set. The data will be read in "while-do" cycle
so that they are not read after an error (kill_test == 1)
or a spurious wake up.

In addition, "reader_finish" is manipulated by the producer thread.
Therefore we add READ_ONCE() to make sure that the fresh value is
read in each cycle. Also we add the corresponding barrier
to synchronize the sleep check.

Next we set the state back to TASK_RUNNING for the situation where we
did not sleep.

Just from paranoid reasons, we initialize both completions statically.
This is safer, in case there are other races that we are unaware of.

As a side effect we could remove the memory barrier from
ring_buffer_producer_thread(). IMHO, this was the reason for
the barrier. ring_buffer_reset() uses spin locks that should
provide the needed memory barrier for using the buffer.

Link: http://lkml.kernel.org/r/1441629518-32712-2-git-send-email-pmladek@suse.comSigned-off-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

TP_ARGS is not used anywhere in trace.h nor trace_entries.h
Firstly, I left just #undef TP_ARGS and had no errors - remove it.

Link: http://lkml.kernel.org/r/1446576560-14085-1-git-send-email-0x7f454c46@gmail.comSigned-off-by: NDmitry Safonov <0x7f454c46@gmail.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>