| Subject: printk: Don't call printk_tick in printk_needs_cpu() on RT |
| From: Yong Zhang <yong.zhang0@gmail.com> |
| Date: Sun, 16 Oct 2011 18:56:45 +0800 |
| |
| printk_tick() can't be called in atomic context when RT is enabled, |
| 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 |
| |
| Now this is a really rare case and it's very unlikely that we starve |
| an logbuf waiter that way. |
| |
| Signed-off-by: Yong Zhang <yong.zhang0@gmail.com> |
| Link: http://lkml.kernel.org/r/1318762607-2261-4-git-send-email-yong.zhang0@gmail.com |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| --- |
| kernel/printk.c | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| --- a/kernel/printk.c |
| +++ b/kernel/printk.c |
| @@ -2030,8 +2030,8 @@ 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); |
| } |
| |
