Messages in this thread |  | | Date | Wed, 6 Feb 2013 22:29:49 +0100 | From | Jan Kara <> | Subject | Re: [PATCH v2] printk: Avoid softlockups in console_unlock() |
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On Wed 06-02-13 12:19:19, Hugh Dickins wrote: > On Wed, 6 Feb 2013, Jan Kara wrote: > > On Wed 06-02-13 09:58:48, David Rientjes wrote: > > > On Wed, 6 Feb 2013, Jan Kara wrote: > > > > > > > Yes, I noticed that thread just yesterday and also though that using > > > > similar trick might be viable. I'll experiment if we could use the same > > > > method for handling lockup problems I hit. Steven seems to have already > > > > tweaked PRINTK_PENDING stuff to be usable more easily... > > > > > > > > > > Are these new build failures in linux-next coming from this patch? > > > > > > kernel/printk.c: In function 'console_unlock': > > > kernel/printk.c:2156:18: error: 'printk_work' undeclared (first use in this function) > > > kernel/printk.c:2156:18: note: each undeclared identifier is reported only once for each function it appears in > > > kernel/printk.c: At top level: > > > kernel/printk.c:2167:13: warning: 'printk_worker' defined but not used [-Wunused-function] > > Yes, I already sent a patch to fix these (attached if you need it). > > Thanks for notice. > > Is the console_unlock patch actually intended to be a console load test? > Could we just revert it until it's baked? Yeah, agreed. I'll probably go sligthly different route anyway.
> This little hunk from __console_unlock(): > > console_may_schedule = 0; > + cur_cpu = smp_processor_id(); > > I have CONFIG_PREEMPT=y CONFIG_DEBUG_PREEMPT=y, > so that fills the console with messages: Thanks for report, I'll take this in consideration when working on the next version of the patch. Somehow console_unlock() was never called from the context you show below in my testing.
> BUG: using smp_processor_id() in preemptible [00000000] code: systemd/1 > caller is __console_unlock+0x3c/0x39c > Pid: 1, comm: systemd Tainted: G W 3.8.0-rc6-mm1 #1 > Call Trace: > [<ffffffff81223ee2>] debug_smp_processor_id+0xbe/0xd8 > [<ffffffff810615d8>] __console_unlock+0x3c/0x39c > [<ffffffff810a6a38>] ? trace_hardirqs_on+0xd/0xf > [<ffffffff8154a997>] ? _raw_spin_unlock_irqrestore+0x46/0x64 > [<ffffffff81061941>] console_unlock+0x9/0x1b > [<ffffffff812955ab>] con_shutdown+0x29/0x2d > [<ffffffff81295582>] ? visual_init+0x10d/0x10d > [<ffffffff812857ed>] release_tty+0x4d/0x91 > [<ffffffff8128644f>] tty_release+0x421/0x460 > [<ffffffff81120c57>] __fput+0x104/0x1e9 > [<ffffffff81120d45>] ____fput+0x9/0xb > [<ffffffff8107a6c3>] task_work_run+0x79/0xa6 > [<ffffffff8102f4a6>] do_notify_resume+0x55/0x66 > [<ffffffff8121e29e>] ? trace_hardirqs_on_thunk+0x3a/0x3f > [<ffffffff8154b898>] int_signal+0x12/0x17
Honza -- Jan Kara <jack@suse.cz> SUSE Labs, CR
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