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Subject[RFC] [PATCH -rt 3/5] printk: don't call printk_tick in printk_needs_cpu()
Date
printk_tick() can't be called in atomic context, otherwise below
warning will show:

[ 117.597095] BUG: sleeping function called from invalid context at kernel/rtmutex.c:645
[ 117.597102] in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: kworker/0:0
[ 117.597111] Pid: 0, comm: kworker/0:0 Not tainted 3.0.6-rt17-00284-gb76d419-dirty #7
[ 117.597116] Call Trace:
[ 117.597131] [<c06e3b61>] ? printk+0x1d/0x24
[ 117.597142] [<c01390b6>] __might_sleep+0xe6/0x110
[ 117.597151] [<c06e634c>] rt_spin_lock+0x1c/0x30
[ 117.597158] [<c0142f26>] __wake_up+0x26/0x60
[ 117.597166] [<c014c78e>] printk_tick+0x3e/0x40
[ 117.597173] [<c014c7b4>] printk_needs_cpu+0x24/0x30
[ 117.597181] [<c017ecc8>] tick_nohz_stop_sched_tick+0x2e8/0x410
[ 117.597191] [<c017305a>] ? sched_clock_idle_wakeup_event+0x1a/0x20
[ 117.597201] [<c010182a>] cpu_idle+0x4a/0xb0
[ 117.597209] [<c06e0b97>] start_secondary+0xd3/0xd7

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
---
kernel/printk.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index 0c9a0ab..a50af4e 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1282,8 +1282,8 @@ void printk_tick(void)

int printk_needs_cpu(int cpu)
{
- if (cpu_is_offline(cpu))
- printk_tick();
+ if (unlikely(cpu_is_offline(cpu)))
+ __this_cpu_write(printk_pending, 0);
return __this_cpu_read(printk_pending);
}

--
1.7.1


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