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Seems that Peter Zijlstra added a new check that is making old

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code screem nasty warnings:
 
 WARNING: CPU: 0 PID: 91 at kernel/sched/core.c:7253 __might_sleep+0x9a/0x378()
 do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffff8d79b511>] event_test_thread+0x48/0x93
 Modules linked in:
 CPU: 0 PID: 91 Comm: test-events Not tainted 3.17.0-rc7-00109-g2f85d18 #37
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
  0000000000000000 ffff880010ec3c80 ffffffff8c696943 ffff880010ec3cb8
  ffffffff8be7cae5 ffffffff8bead236 0000000000000001 ffff88001161fa01
  0000000000000001 0000000000000000 ffff880010ec3d20 ffffffff8be7cb46
 Call Trace:
  [<ffffffff8c696943>] dump_stack+0x19/0x1b
  [<ffffffff8be7cae5>] warn_slowpath_common+0x8f/0xa8
  [<ffffffff8bead236>] ? __might_sleep+0x9a/0x378
  [<ffffffff8be7cb46>] warn_slowpath_fmt+0x48/0x50
  [<ffffffff8be0dd55>] ? sched_clock+0x9/0xd
  [<ffffffff8d79b511>] ? event_test_thread+0x48/0x93
  [<ffffffff8d79b511>] ? event_test_thread+0x48/0x93
  [<ffffffff8bead236>] __might_sleep+0x9a/0x378
  [<ffffffff8c6a0227>] down_read+0x26/0x98
  [<ffffffff8be8f503>] exit_signals+0x27/0x1c2
  [<ffffffff8be7fedd>] do_exit+0x193/0x10bd
  [<ffffffff8bfd1969>] ? kfree+0x4a0/0x4d7
  [<ffffffff8d79b4c9>] ? event_trace_self_tests+0x6d7/0x6d7
  [<ffffffff8d79b4c9>] ? event_trace_self_tests+0x6d7/0x6d7
  [<ffffffff8bea4b65>] kthread+0x156/0x156
  [<ffffffff8c69c0f8>] ? wait_for_common+0x3e/0x224
  [<ffffffff8bea4a0f>] ? insert_kthread_work+0xe7/0xe7
  [<ffffffff8c6a353a>] ret_from_fork+0x7a/0xb0
  [<ffffffff8bea4a0f>] ? insert_kthread_work+0xe7/0xe7
 ---[ end trace 14d02ef17adbc114 ]---
 
 These are triggered by some self tests that run at start up when
 configure in. Although the code is technically correct, they are a little
 sloppy and not very robust. They work now because it runs at boot up
 and the tests do not call anything that might trigger a spurious
 wake up. But that doesn't mean those tests wont change in the future.
 
 It's best to clean them now to make sure the tests used to test the
 internal workings of the system don't cause breakage themselves.
 
 This also quiets the warnings made by the new checks.
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Merge tag 'trace-3.18-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
 "Seems that Peter Zijlstra added a new check that is making old code
  scream nasty warnings:

    WARNING: CPU: 0 PID: 91 at kernel/sched/core.c:7253 __might_sleep+0x9a/0x378()
    do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffff8d79b511>] event_test_thread+0x48/0x93
    Call Trace:
      __might_sleep+0x9a/0x378
      down_read+0x26/0x98
      exit_signals+0x27/0x1c2
      do_exit+0x193/0x10bd
      kthread+0x156/0x156
      ret_from_fork+0x7a/0xb0

  These are triggered by some self tests that run at start up when
  configure in.  Although the code is technically correct, they are a
  little sloppy and not very robust.  They work now because it runs at
  boot up and the tests do not call anything that might trigger a
  spurious wake up.  But that doesn't mean those tests wont change in
  the future.

  It's best to clean them now to make sure the tests used to test the
  internal workings of the system don't cause breakage themselves.

  This also quiets the warnings made by the new checks"

* tag 'trace-3.18-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Clean up scheduling in trace_wakeup_test_thread()
  tracing: Robustify wait loop
This commit is contained in:
Linus Torvalds 2014-10-12 07:28:55 -04:00
commit 8df6be116c
2 changed files with 34 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
kernel/trace/trace_events.c
View File

@ -2513,8 +2513,11 @@ static __init int event_test_thread(void *unused)
kfree(test_malloc);
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop())
while (!kthread_should_stop()) {
schedule();
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
return 0;
}

47
kernel/trace/trace_selftest.c
View File

@ -1029,6 +1029,12 @@ trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr)
#endif
#ifdef CONFIG_SCHED_TRACER
struct wakeup_test_data {
struct completion is_ready;
int go;
};
static int trace_wakeup_test_thread(void *data)
{
/* Make this a -deadline thread */
@ -1038,51 +1044,56 @@ static int trace_wakeup_test_thread(void *data)
.sched_deadline = 10000000ULL,
.sched_period = 10000000ULL
};
struct completion *x = data;
struct wakeup_test_data *x = data;
sched_setattr(current, &attr);
/* Make it know we have a new prio */
complete(x);
complete(&x->is_ready);
/* now go to sleep and let the test wake us up */
set_current_state(TASK_INTERRUPTIBLE);
schedule();
while (!x->go) {
schedule();
set_current_state(TASK_INTERRUPTIBLE);
}
complete(x);
complete(&x->is_ready);
set_current_state(TASK_INTERRUPTIBLE);
/* we are awake, now wait to disappear */
while (!kthread_should_stop()) {
/*
* This will likely be the system top priority
* task, do short sleeps to let others run.
*/
msleep(100);
schedule();
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
return 0;
}
int
trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
{
unsigned long save_max = tr->max_latency;
struct task_struct *p;
struct completion is_ready;
struct wakeup_test_data data;
unsigned long count;
int ret;
init_completion(&is_ready);
memset(&data, 0, sizeof(data));
init_completion(&data.is_ready);
/* create a -deadline thread */
p = kthread_run(trace_wakeup_test_thread, &is_ready, "ftrace-test");
p = kthread_run(trace_wakeup_test_thread, &data, "ftrace-test");
if (IS_ERR(p)) {
printk(KERN_CONT "Failed to create ftrace wakeup test thread ");
return -1;
}
/* make sure the thread is running at -deadline policy */
wait_for_completion(&is_ready);
wait_for_completion(&data.is_ready);
/* start the tracing */
ret = tracer_init(trace, tr);
@ -1103,18 +1114,20 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
msleep(100);
}
init_completion(&is_ready);
init_completion(&data.is_ready);
data.go = 1;
/* memory barrier is in the wake_up_process() */
wake_up_process(p);
/* Wait for the task to wake up */
wait_for_completion(&is_ready);
wait_for_completion(&data.is_ready);
/* stop the tracing. */
tracing_stop();
/* check both trace buffers */
ret = trace_test_buffer(&tr->trace_buffer, NULL);
printk("ret = %d\n", ret);
if (!ret)
ret = trace_test_buffer(&tr->max_buffer, &count);