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  1. 13 3月, 2010 5 次提交
    • S
      tracing: Do not record user stack trace from NMI context · b6345879
      由 Steven Rostedt 提交于 
      A bug was found with Li Zefan's ftrace_stress_test that caused applications
to segfault during the test.

Placing a tracing_off() in the segfault code, and examining several
traces, I found that the following was always the case. The lock tracer
was enabled (lockdep being required) and userstack was enabled. Testing
this out, I just enabled the two, but that was not good enough. I needed
to run something else that could trigger it. Running a load like hackbench
did not work, but executing a new program would. The following would
trigger the segfault within seconds:

  # echo 1 > /debug/tracing/options/userstacktrace
  # echo 1 > /debug/tracing/events/lock/enable
  # while :; do ls > /dev/null ; done

Enabling the function graph tracer and looking at what was happening
I finally noticed that all cashes happened just after an NMI.

 1)               |    copy_user_handle_tail() {
 1)               |      bad_area_nosemaphore() {
 1)               |        __bad_area_nosemaphore() {
 1)               |          no_context() {
 1)               |            fixup_exception() {
 1)   0.319 us    |              search_exception_tables();
 1)   0.873 us    |            }
[...]
 1)   0.314 us    |  __rcu_read_unlock();
 1)   0.325 us    |    native_apic_mem_write();
 1)   0.943 us    |  }
 1)   0.304 us    |  rcu_nmi_exit();
[...]
 1)   0.479 us    |  find_vma();
 1)               |  bad_area() {
 1)               |    __bad_area() {

After capturing several traces of failures, all of them happened
after an NMI. Curious about this, I added a trace_printk() to the NMI
handler to read the regs->ip to see where the NMI happened. In which I
found out it was here:

ffffffff8135b660 <page_fault>:
ffffffff8135b660:       48 83 ec 78             sub    $0x78,%rsp
ffffffff8135b664:       e8 97 01 00 00          callq  ffffffff8135b800 <error_entry>

What was happening is that the NMI would happen at the place that a page
fault occurred. It would call rcu_read_lock() which was traced by
the lock events, and the user_stack_trace would run. This would trigger
a page fault inside the NMI. I do not see where the CR2 register is
saved or restored in NMI handling. This means that it would corrupt
the page fault handling that the NMI interrupted.

The reason the while loop of ls helped trigger the bug, was that
each execution of ls would cause lots of pages to be faulted in, and
increase the chances of the race happening.

The simple solution is to not allow user stack traces in NMI context.
After this patch, I ran the above "ls" test for a couple of hours
without any issues. Without this patch, the bug would trigger in less
than a minute.

Cc: stable@kernel.org
Reported-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      b6345879
    • S
      tracing: Disable buffer switching when starting or stopping trace · a2f80714
      由 Steven Rostedt 提交于 
      When the trace iterator is read, tracing_start() and tracing_stop()
is called to stop tracing while the iterator is processing the trace
output.

These functions disable both the standard buffer and the max latency
buffer. But if the wakeup tracer is running, it can switch these
buffers between the two disables:

  buffer = global_trace.buffer;
  if (buffer)
      ring_buffer_record_disable(buffer);

      <<<--------- swap happens here

  buffer = max_tr.buffer;
  if (buffer)
      ring_buffer_record_disable(buffer);

What happens is that we disabled the same buffer twice. On tracing_start()
we can enable the same buffer twice. All ring_buffer_record_disable()
must be matched with a ring_buffer_record_enable() or the buffer
can be disable permanently, or enable prematurely, and cause a bug
where a reset happens while a trace is commiting.

This patch protects these two by taking the ftrace_max_lock to prevent
a switch from occurring.

Found with Li Zefan's ftrace_stress_test.

Cc: stable@kernel.org
Reported-by: NLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      a2f80714
    • S
      tracing: Use same local variable when resetting the ring buffer · 283740c6
      由 Steven Rostedt 提交于 
      In the ftrace code that resets the ring buffer it references the
buffer with a local variable, but then uses the tr->buffer as the
parameter to reset. If the wakeup tracer is running, which can
switch the tr->buffer with the max saved buffer, this can break
the requirement of disabling the buffer before the reset.

   buffer = tr->buffer;
   ring_buffer_record_disable(buffer);
   synchronize_sched();
   __tracing_reset(tr->buffer, cpu);

If the tr->buffer is swapped, then the reset is not happening to the
buffer that was disabled. This will cause the ring buffer to fail.

Found with Li Zefan's ftrace_stress_test.

Cc: stable@kernel.org
Reported-by: NLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      283740c6
    • S
      function-graph: Init curr_ret_stack with ret_stack · ea14eb71
      由 Steven Rostedt 提交于 
      If the graph tracer is active, and a task is forked but the allocating of
the processes graph stack fails, it can cause crash later on.

This is due to the temporary stack being NULL, but the curr_ret_stack
variable is copied from the parent. If it is not -1, then in
ftrace_graph_probe_sched_switch() the following:

	for (index = next->curr_ret_stack; index >= 0; index--)
		next->ret_stack[index].calltime += timestamp;

Will cause a kernel OOPS.

Found with Li Zefan's ftrace_stress_test.

Cc: stable@kernel.org
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      ea14eb71
    • L
      ring-buffer: Move disabled check into preempt disable section · 52fbe9cd
      由 Lai Jiangshan 提交于 
      The ring buffer resizing and resetting relies on a schedule RCU
action. The buffers are disabled, a synchronize_sched() is called
and then the resize or reset takes place.

But this only works if the disabling of the buffers are within the
preempt disabled section, otherwise a window exists that the buffers
can be written to while a reset or resize takes place.

Cc: stable@kernel.org
Reported-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4B949E43.2010906@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      52fbe9cd
  3. 11 3月, 2010 1 次提交
  5. 06 3月, 2010 4 次提交
    • T
      function-graph: Add tracing_thresh support to function_graph tracer · 0e950173
      由 Tim Bird 提交于 
      Add support for tracing_thresh to the function_graph tracer.  This
version of this feature isolates the checks into new entry and
return functions, to avoid adding more conditional code into the
main function_graph paths.

When the tracing_thresh is set and the function graph tracer is
enabled, only the functions that took longer than the time in
microseconds that was set in tracing_thresh are recorded. To do this
efficiently, only the function exits are recorded:

 [tracing]# echo 100 > tracing_thresh
 [tracing]# echo function_graph > current_tracer
 [tracing]# cat trace
 # tracer: function_graph
 #
 # CPU  DURATION                  FUNCTION CALLS
 # |     |   |                     |   |   |   |
  1) ! 119.214 us  |  } /* smp_apic_timer_interrupt */
  1)   <========== |
  0) ! 101.527 us  |              } /* __rcu_process_callbacks */
  0) ! 126.461 us  |            } /* rcu_process_callbacks */
  0) ! 145.111 us  |          } /* __do_softirq */
  0) ! 149.667 us  |        } /* do_softirq */
  0) ! 168.817 us  |      } /* irq_exit */
  0) ! 248.254 us  |    } /* smp_apic_timer_interrupt */

Also, add support for specifying tracing_thresh on the kernel
command line.  When used like so: "tracing_thresh=200 ftrace=function_graph"
this can be used to analyse system startup.  It is important to disable
tracing soon after boot, in order to avoid losing the trace data.
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NTim Bird <tim.bird@am.sony.com>
LKML-Reference: <4B87098B.4040308@am.sony.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      0e950173
    • A
      tracing: Update the comm field in the right variable in update_max_tr · 1acaa1b2
      由 Arnaldo Carvalho de Melo 提交于 
      The latency output showed:

 #    | task: -3 (uid:0 nice:0 policy:1 rt_prio:99)

The comm is missing in the "task:" and it looks like a minus 3 is
the output. The correct display should be:

 #    | task: migration/0-3 (uid:0 nice:0 policy:1 rt_prio:99)

The problem is that the comm is being stored in the wrong data
structure. The max_tr.data[cpu] is what stores the comm, not the
tr->data[cpu].

Before this patch the max_tr.data[cpu]->comm was zeroed and the /debug/trace
ended up showing just the '-' sign followed by the pid.

Also remove a needless initialization of max_data.
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <1267824230-23861-1-git-send-email-acme@infradead.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      1acaa1b2
    • S
      function-graph: Use comment notation for func names of dangling '}' · a094fe04
      由 Steven Rostedt 提交于 
      When a '}' does not have a matching function start, the name is printed
within parenthesis. But this makes it confusing between ending '}'
and function starts. This patch makes the function name appear in C comment
notation.

Old view:
 3)   1.281 us    |            } (might_fault)
 3)   3.620 us    |          } (filldir)
 3)   5.251 us    |        } (call_filldir)
 3)               |        call_filldir() {
 3)               |          filldir() {

New view:
 3)   1.281 us    |            } /* might_fault */
 3)   3.620 us    |          } /* filldir */
 3)   5.251 us    |        } /* call_filldir */
 3)               |        call_filldir() {
 3)               |          filldir() {
Requested-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      a094fe04
    • S
      function-graph: Fix unused reference to ftrace_set_func() · 801c29fd
      由 Steven Rostedt 提交于 
      The declaration of ftrace_set_func() is at the start of the ftrace.c file
and wrapped with a #ifdef CONFIG_FUNCTION_GRAPH condition. If function
graph tracing is enabled but CONFIG_DYNAMIC_FTRACE is not, a warning
about that function being declared static and unused is given.

This really should have been placed within the CONFIG_FUNCTION_GRAPH
condition that uses ftrace_set_func().

Moving the declaration down fixes the warning and makes the code cleaner.
Reported-by: NPeter Zijlstra <peterz@infradead.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      801c29fd
  7. 04 3月, 2010 1 次提交
  9. 03 3月, 2010 5 次提交
    • L
      tracing: Fix warning in s_next of trace file ops · ac91d854
      由 Lai Jiangshan 提交于 
      This warning in s_next() can be triggered by lseek():
 [<c018b3f7>] ? s_next+0x77/0x80
 [<c013e3c1>] warn_slowpath_common+0x81/0xa0
 [<c018b3f7>] ? s_next+0x77/0x80
 [<c013e3fa>] warn_slowpath_null+0x1a/0x20
 [<c018b3f7>] s_next+0x77/0x80
 [<c01efa77>] traverse+0x117/0x200
 [<c01eff13>] seq_lseek+0xa3/0x120
 [<c01efe70>] ? seq_lseek+0x0/0x120
 [<c01d7081>] vfs_llseek+0x41/0x50
 [<c01d8116>] sys_llseek+0x66/0xa0
 [<c0102bd0>] sysenter_do_call+0x12/0x26

The iterator "leftover" variable is zeroed in the opening of the trace
file. But lseek can call s_start() which will call s_next() without
reseting the "leftover" variable back to zero, which might trigger
the WARN_ON_ONCE(iter->leftover) that is in s_next().

Cc: stable@kernel.org
Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4B8CE06A.9090207@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      ac91d854
    • L
      Merge branch 'for-linus' of git://gitorious.org/linux-omap-dss2/linux · 3a5b27bf
      由 Linus Torvalds 提交于 
      * 'for-linus' of git://gitorious.org/linux-omap-dss2/linux: (49 commits)
  OMAP: DSS2: Taal: Fix TE when resuming
  OMAP: DSS2: Taal: Fix ESD check
  OMAP: DSS2: OMAPFB: Constify some function parameters
  OMAP: DSS2: OMAPFB: install omapfb.h
  OMAP: DSS2: DSI: add error prints
  OMAP: DSS2: TPO-TD03MTEA1: fix function names
  OMAP: DSS2: DSI: add dsi_vc_dcs_read_2() helper
  OMAP: DSS2: OMAPFB: Remove FB_OMAP2_FORCE_AUTO_UPDATE
  OMAP: DSS2: DSI: remove external TE support
  OMAP: DSS2: move timing functions
  OMAP: DSS2: move set/get_wss()
  OMAP: DSS2: move enable/disable/suspend/resume
  OMAP: DSS2: move update() and sync()
  OMAP: DSS2: move set/get_update_mode()
  OMAP: DSS2: move enable/get_te()
  OMAP: DSS2: move get_recommended_bpp()
  OMAP: DSS2: move get_resolution()
  OMAP: DSS2: move enable/disable_channel to overlay manager
  OMAP: DSS2: move wait_vsync()
  OMAP: DSS2: move get/set_rotate()
  ...
      3a5b27bf
    • L
      Merge branch 'omap-for-linus' of... · 5057bfaf
      由 Linus Torvalds 提交于 
      Merge branch 'omap-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap-2.6

* 'omap-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap-2.6: (214 commits)
  omap2: Initialize Menelaus and MMC for N8X0
  AM3517 EVM: correct typo - tca6416 mispelt as tca6516
  AM3517 EVM: Enable I2C support
  AM35x: Enable OMAP_MUX in defconfig
  AM35x: Add missing GPIO mux config for EHCI port
  Zoom3: Defconfig update
  omap: i2c: Fix muxing for command line enabled bus
  OMAP4: clock: Remove clock hacks from timer-gp.c
  OMAP4: clock: Add dummy clock nodes for interface clocks
  OMAP4: clock: Rename leaf clock nodes to end with a _ick or _fck
  OMAP2+ clock: revise omap2_clk_{disable,enable}()
  OMAP2/3 clock: combine OMAP2 & 3 boot-time MPU rate change code
  OMAP clockdomain: if no autodeps exist, don't try to add or remove them
  OMAP hwmod: add hwmod class support
  OMAP hwmod: convert header files with static allocations into C files
  OMAP hwmod: convert hwmod to use hardware clock names rather than clkdev dev+con
  OMAP clock: add omap_clk_get_by_name() for use by OMAP hwmod core code
  OMAP3: clock: add capability to change rate of dpll4_m5_ck_3630
  OMAP4 clock: drop the ALWAYS_ENABLED clock flag
  OMAP clock: drop RATE_FIXED clock flag
  ...
      5057bfaf
    • L
      Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block · 6c0ad5df
      由 Linus Torvalds 提交于 
      * 'for-linus' of git://git.kernel.dk/linux-2.6-block:
  Revert "blkdev: fix merge_bvec_fn return value checks"
      6c0ad5df
    • J
      Revert "blkdev: fix merge_bvec_fn return value checks" · 9599945b
      由 Jens Axboe 提交于 
      This reverts commit 9f7cdbc3.

It's causing oopses om dm setups, so revert it until we investigate.
Reported-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Tested-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
      9599945b
  11. 02 3月, 2010 24 次提交