2012-10-24 14:29:13 +00:00
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Subject: printk: Don't call printk_tick in printk_needs_cpu() on RT
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2011-11-20 00:01:55 +00:00
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From: Yong Zhang <yong.zhang0@gmail.com>
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Date: Sun, 16 Oct 2011 18:56:45 +0800
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printk_tick() can't be called in atomic context when RT is enabled,
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otherwise below warning will show:
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[ 117.597095] BUG: sleeping function called from invalid context at kernel/rtmutex.c:645
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[ 117.597102] in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: kworker/0:0
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[ 117.597111] Pid: 0, comm: kworker/0:0 Not tainted 3.0.6-rt17-00284-gb76d419-dirty #7
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[ 117.597116] Call Trace:
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[ 117.597131] [<c06e3b61>] ? printk+0x1d/0x24
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[ 117.597142] [<c01390b6>] __might_sleep+0xe6/0x110
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[ 117.597151] [<c06e634c>] rt_spin_lock+0x1c/0x30
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[ 117.597158] [<c0142f26>] __wake_up+0x26/0x60
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[ 117.597166] [<c014c78e>] printk_tick+0x3e/0x40
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[ 117.597173] [<c014c7b4>] printk_needs_cpu+0x24/0x30
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[ 117.597181] [<c017ecc8>] tick_nohz_stop_sched_tick+0x2e8/0x410
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[ 117.597191] [<c017305a>] ? sched_clock_idle_wakeup_event+0x1a/0x20
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[ 117.597201] [<c010182a>] cpu_idle+0x4a/0xb0
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[ 117.597209] [<c06e0b97>] start_secondary+0xd3/0xd7
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Now this is a really rare case and it's very unlikely that we starve
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an logbuf waiter that way.
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Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
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Link: http://lkml.kernel.org/r/1318762607-2261-4-git-send-email-yong.zhang0@gmail.com
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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kernel/printk.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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2012-10-24 14:29:13 +00:00
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Index: linux-stable/kernel/printk.c
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===================================================================
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--- linux-stable.orig/kernel/printk.c
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+++ linux-stable/kernel/printk.c
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@@ -2027,8 +2027,8 @@ void printk_tick(void)
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2011-11-20 00:01:55 +00:00
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int printk_needs_cpu(int cpu)
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{
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- if (cpu_is_offline(cpu))
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- printk_tick();
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+ if (unlikely(cpu_is_offline(cpu)))
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+ __this_cpu_write(printk_pending, 0);
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return __this_cpu_read(printk_pending);
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}
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