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From: Lai Jiangshan on 16 Mar 2010 05:10
tracepoint.h use rcu_dereference(), it triggers this warning:

[ 0.701161] ===================================================
[ 0.702211] [ INFO: suspicious rcu_dereference_check() usage. ]
[ 0.702716] ---------------------------------------------------
[ 0.703203] include/trace/events/workqueue.h:68 invoked rcu_dereference_check() without protection!
[ 0.703971]
[ 0.703990] other info that might help us debug this:
[ 0.703993]
[ 0.705590]
[ 0.705604] rcu_scheduler_active = 1, debug_locks = 0
[ 0.706712] 1 lock held by swapper/1:
[ 0.707229] #0: (cpu_add_remove_lock){+.+.+.}, at: [<c0142f54>] cpu_maps_update_begin+0x14/0x20
[ 0.710097]
[ 0.710106] stack backtrace:
[ 0.712602] Pid: 1, comm: swapper Not tainted 2.6.34-rc1-tip-01613-g72662bb #168
[ 0.713231] Call Trace:
[ 0.713997] [<c017174d>] lockdep_rcu_dereference+0x9d/0xb0
[ 0.714746] [<c015a117>] create_workqueue_thread+0x107/0x110
[ 0.715353] [<c015aee0>] ? worker_thread+0x0/0x340
[ 0.715845] [<c015a8e8>] __create_workqueue_key+0x138/0x240
[ 0.716427] [<c0142f92>] ? cpu_maps_update_done+0x12/0x20
[ 0.717012] [<c086b12f>] init_workqueues+0x6f/0x80
[ 0.717530] [<c08576d2>] kernel_init+0x102/0x1f0
[ 0.717570] [<c08575d0>] ? kernel_init+0x0/0x1f0
[ 0.718944] [<c01030fa>] kernel_thread_helper+0x6/0x10

Signed-off-by: Lai Jiangshan <laijs(a)cn.fujitsu.com>
---
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index f59604e..78b4bd3 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -49,7 +49,7 @@ struct tracepoint {
void **it_func; \
\
rcu_read_lock_sched_notrace(); \
- it_func = rcu_dereference((tp)->funcs); \
+ it_func = rcu_dereference_sched((tp)->funcs); \
if (it_func) { \
do { \
((void(*)(proto))(*it_func))(args); \

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Prev: Remove GENHD_FL_DRIVERFS
Next: [PATCH] gpio: max732x: fix input configuration for open-drain pins