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Subject[PATCH 3/3] vmevent: Should not grab mutex in the atomic context
There is not need to grab mutex in the atomic context, moreover this is
wrong and causes the following bug:

BUG: sleeping function called from invalid context at kernel/mutex.c:271
in_atomic(): 1, irqs_disabled(): 1, pid: 1056, name: m
no locks held by m/1056.
irq event stamp: 58768
hardirqs last enabled at (58767): [<ffffffff8101ca35>] do_page_fault+0x275/0x450
hardirqs last disabled at (58768): [<ffffffff81325a2b>] apic_timer_interrupt+0x6b/0x80
softirqs last enabled at (58676): [<ffffffff81038def>] __do_softirq+0x10f/0x160
softirqs last disabled at (58671): [<ffffffff813262ac>] call_softirq+0x1c/0x26
Pid: 1056, comm: m Not tainted 3.2.0+ #3
Call Trace:
<IRQ> [<ffffffff81062530>] ? print_irqtrace_events+0xd0/0xe0
[<ffffffff8102f5da>] __might_sleep+0x12a/0x1e0
[<ffffffff81321dbc>] mutex_lock_nested+0x3c/0x340
[<ffffffff81053a8c>] ? __run_hrtimer+0x4c/0x100
[<ffffffff810bd920>] ? vmevent_read+0x100/0x100
[<ffffffff810bd79e>] vmevent_sample+0x6e/0xf0
[<ffffffff810bd946>] vmevent_timer_fn+0x26/0x60
[<ffffffff81053a92>] __run_hrtimer+0x52/0x100
[<ffffffff81054463>] hrtimer_interrupt+0xf3/0x220
[<ffffffff810166d4>] smp_apic_timer_interrupt+0x64/0xa0
[<ffffffff81325a30>] apic_timer_interrupt+0x70/0x80
<EOI> [<ffffffff8101ca3a>] ? do_page_fault+0x27a/0x450
[<ffffffff8101ca35>] ? do_page_fault+0x275/0x450
[<ffffffff810036bf>] ? do_softirq+0x6f/0xc0
[<ffffffff8132485d>] ? retint_restore_args+0xe/0xe
[<ffffffff8132484a>] ? retint_swapgs+0xe/0x13
[<ffffffff8116b31d>] ? trace_hardirqs_off_thunk+0x3a/0x3c
[<ffffffff81324a3f>] page_fault+0x1f/0x30
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
The patch is for git://github.com/penberg/linux.git vmevent/core.

mm/vmevent.c | 4 ----
1 files changed, 0 insertions(+), 4 deletions(-)
diff --git a/mm/vmevent.c b/mm/vmevent.c
index 1375f9d..1dbefb5 100644
--- a/mm/vmevent.c
+++ b/mm/vmevent.c
@@ -71,8 +71,6 @@ static void vmevent_sample(struct vmevent_watch *watch)
if (!vmevent_match(watch, &event))
return;

- mutex_lock(&watch->mutex);
-
watch->pending = true;

if (watch->config.event_attrs & VMEVENT_EATTR_NR_AVAIL_PAGES)
@@ -85,8 +83,6 @@ static void vmevent_sample(struct vmevent_watch *watch)
watch->attr_values[n++] = event.nr_swap_pages;

watch->nr_attrs = n;
-
- mutex_unlock(&watch->mutex);
}

static enum hrtimer_restart vmevent_timer_fn(struct hrtimer *hrtimer)
--
1.7.7.6

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