[PATCH] hrtimer:__run_hrtimer races with enqueue_hrtimer
From: he, bo
Date: Thu Oct 25 2012 - 22:56:21 EST
From: Yanmin Zhang <yanmin.zhang@xxxxxxxxx>
We hit a kernel panic at __run_hrtimer=>BUG_ON(timer->state != HRTIMER_STATE_CALLBACK).
<2>[ 10.226053, 3] kernel BUG at /home/android/xiaobing/ymz/r4/hardware/intel/linux-2.6/kernel/hrtimer.c:1228!
<0>[ 10.235682, 3] invalid opcode: 0000 [#1] PREEMPT SMP
<4>[ 10.240716, 3] Modules linked in: wl12xx_sdio wl12xx mac80211 cfg80211 compat btwilink rmi4(C) fmdrv_chr st_drv matrix(C)
<4>[ 10.251651, 3]
<4>[ 10.253391, 3] Pid: 68, comm: kworker/3:4 Tainted: G WC 3.0.34-140430-g2af538d #45 Intel Corporation CloverTrail/FFRD
<4>[ 10.264674, 3] EIP: 0060:[<c126c7ed>] EFLAGS: 00010002 CPU: 3
<4>[ 10.270411, 3] EIP is at __run_hrtimer+0xbd/0x240
<4>[ 10.275091, 3] EAX: 00000001 EBX: f67fb6b8 ECX: f57b4000 EDX: 00007301
<4>[ 10.281602, 3] ESI: c1d614c0 EDI: f67fb680 EBP: f57b5dd8 ESP: f57b5da8
<4>[ 10.288113, 3] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
<0>[ 10.293754, 3] Process kworker/3:4 (pid: 68, ti=f57b4000 task=f57aa730 task.ti=f57b4000)
<0>[ 10.301827, 3] Stack:
<4>[ 10.304083, 3] 00000000 c1afef40 f57b5dd8 c167a6e0 f67fb680 20b366e3 f67fb6b8 f57b5e14
<4>[ 10.312069, 3] 00000001 f67fb6b8 00000001 f67fb680 f57b5e28 c126d1e5 f57b5e08 c126f325
<4>[ 10.320055, 3] 00000000 86b9868d 00000001 86b9868d 00000001 00000003 ffffffff 7fffffff
<0>[ 10.328041, 3] Call Trace:
<4>[ 10.330742, 3] [<c167a6e0>] ? gburst_thread_stop.isra.25+0x40/0x40
<4>[ 10.336988, 3] [<c126d1e5>] hrtimer_interrupt+0xd5/0x250
<4>[ 10.342368, 3] [<c126f325>] ? sched_clock_cpu+0xe5/0x150
<4>[ 10.347753, 3] [<c1871d44>] smp_apic_timer_interrupt+0x54/0x88
<4>[ 10.353654, 3] [<c1496558>] ? trace_hardirqs_off_thunk+0xc/0x14
<4>[ 10.359643, 3] [<c186be9f>] apic_timer_interrupt+0x2f/0x34
<4>[ 10.365199, 3] [<c186e60f>] ? sub_preempt_count+0x1f/0x50
<4>[ 10.370669, 3] [<c149558a>] delay_tsc+0x3a/0xc0
<6>[ 10.371589, 0] android_work: did not send uevent (0 0 (null))
<4>[ 10.381171, 3] [<c14954e3>] __const_udelay+0x23/0x30
<4>[ 10.386207, 3] [<c16d043a>] mdfld_dsi_send_dcs+0x12a/0x5d0
<4>[ 10.391760, 3] [<c186b6c6>] ? _raw_spin_unlock_irqrestore+0x26/0x50
<4>[ 10.398101, 3] [<c16af431>] ? ospm_power_using_hw_begin+0xa1/0x350
<4>[ 10.399053, 3] [<c186a49f>] ? __mutex_lock_slowpath+0x1ff/0x2f0
<4>[ 10.399069, 3] [<c16bd59e>] mdfld_dbi_update_panel+0x21e/0x2d0
<4>[ 10.399085, 3] [<c16b1ae1>] mdfld_te_handler_work+0x71/0x80
<4>[ 10.399099, 3] [<c12642be>] process_one_work+0xfe/0x3f0
<4>[ 10.399114, 3] [<c16b1a70>] ? mdfld_async_flip_te_handler+0xf0/0xf0
Basically, __run_hrtimer has a race with enqueue_hrtimer. When __run_hrtimer calls
the timer callback fn, another thread might call enqueue_hrtimer or hrtimer_start
to requeue it, and the timer->state is equal to HRTIMER_STATE_CALLBACK|HRTIMER_STATE_ENQUEUED,
which causes the BUG_ON(timer->state != HRTIMER_STATE_CALLBACK) checking fails.
The patch fixes it by checking only bit HRTIMER_STATE_CALLBACK.
Signed-off-by: Yanmin Zhang <yanmin.zhang@xxxxxxxxx>
Reviewed-by: He, Bo <bo.he@xxxxxxxxx>
---
kernel/hrtimer.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 6db7a5e..6280184 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1235,7 +1235,7 @@ static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
* hrtimer_start_range_ns() or in hrtimer_interrupt()
*/
if (restart != HRTIMER_NORESTART) {
- BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
+ BUG_ON(!(timer->state & HRTIMER_STATE_CALLBACK));
enqueue_hrtimer(timer, base);
}
--
1.7.6
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