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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2008-08-20 03:31:26 -0400
committerIngo Molnar <mingo@elte.hu>2008-08-20 06:22:37 -0400
commitfa33507a22623b3bd543b15a21c362cf364b6cff (patch)
tree8d77dfaad0336c5591383df1029567d7e6c17bbd /kernel/printk.c
parentced9cd40ac14111befd6b0c73ec90106c22a3fd7 (diff)
printk: robustify printk, fix #2
Dmitry Adamushko reported: > [*] btw., with DEBUG being enabled, pr_debug() generates [1] when > debug_smp_processor_id() is used (CONFIG_DEBUG_PREEMPT). > > the problem seems to be caused by the following commit: > commit b845b517b5e3706a3729f6ea83b88ab85f0725b0 > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > Date: Fri Aug 8 21:47:09 2008 +0200 > > printk: robustify printk > > > wake_up_klogd() -> __get_cpu_var() -> smp_processor_id() > > and that's being called from release_console_sem() which is, in turn, > said to be "may be called from any context" [2] > > and in this case, it seems to be called from some non-preemptible > context (although, it can't be printk()... > although, I haven't looked carefully yet). > > Provided [2], __get_cpu_var() is perhaps not the right solution there. > > > [1] > > [ 7697.942005] BUG: using smp_processor_id() in preemptible [00000000] code: syslogd/3542 > [ 7697.942005] caller is wake_up_klogd+0x1b/0x50 > [ 7697.942005] Pid: 3542, comm: syslogd Not tainted 2.6.27-rc3-tip-git #2 > [ 7697.942005] Call Trace: > [ 7697.942005] [<ffffffff8036b398>] debug_smp_processor_id+0xe8/0xf0 > [ 7697.942005] [<ffffffff80239d3b>] wake_up_klogd+0x1b/0x50 > [ 7697.942005] [<ffffffff8023a047>] release_console_sem+0x1e7/0x200 > [ 7697.942005] [<ffffffff803c0f17>] do_con_write+0xb7/0x1f30 > [ 7697.942005] [<ffffffff8020d920>] ? show_trace+0x10/0x20 > [ 7697.942005] [<ffffffff8020dc42>] ? dump_stack+0x72/0x80 > [ 7697.942005] [<ffffffff8036392d>] ? __ratelimit+0xbd/0xe0 > [ 7697.942005] [<ffffffff8036b398>] ? debug_smp_processor_id+0xe8/0xf0 > [ 7697.942005] [<ffffffff80239d3b>] ? wake_up_klogd+0x1b/0x50 > [ 7697.942005] [<ffffffff8023a047>] ? release_console_sem+0x1e7/0x200 > [ 7697.942005] [<ffffffff803c2de9>] con_write+0x19/0x30 > [ 7697.942005] [<ffffffff803b37b6>] write_chan+0x276/0x3c0 > [ 7697.942005] [<ffffffff80232b20>] ? default_wake_function+0x0/0x10 > [ 7697.942005] [<ffffffff804cb872>] ? _spin_lock_irqsave+0x22/0x50 > [ 7697.942005] [<ffffffff803b1334>] tty_write+0x194/0x260 > [ 7697.942005] [<ffffffff803b3540>] ? write_chan+0x0/0x3c0 > [ 7697.942005] [<ffffffff803b14a4>] redirected_tty_write+0xa4/0xb0 > [ 7697.942005] [<ffffffff803b1400>] ? redirected_tty_write+0x0/0xb0 > [ 7697.942005] [<ffffffff802a88c2>] do_loop_readv_writev+0x52/0x80 > [ 7697.942005] [<ffffffff802a939d>] do_readv_writev+0x1bd/0x1d0 > [ 7697.942005] [<ffffffff802a93e9>] vfs_writev+0x39/0x60 > [ 7697.942005] [<ffffffff802a9870>] sys_writev+0x50/0x90 > [ 7697.942005] [<ffffffff8020bb3b>] system_call_fastpath+0x16/0x1b Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Reported-by: Dmitry Adamushko <dmitry.adamushko@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/printk.c')
-rw-r--r--kernel/printk.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/printk.c b/kernel/printk.c
index 655cc2ca10cc..57e9cd7a9581 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1000,7 +1000,7 @@ int printk_needs_cpu(int cpu)
1000void wake_up_klogd(void) 1000void wake_up_klogd(void)
1001{ 1001{
1002 if (waitqueue_active(&log_wait)) 1002 if (waitqueue_active(&log_wait))
1003 __get_cpu_var(printk_pending) = 1; 1003 __raw_get_cpu_var(printk_pending) = 1;
1004} 1004}
1005 1005
1006/** 1006/**