From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Viresh Kumar <viresh.kumar@linaro.org>, Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Jan Kara <jack@suse.com>, Tejun Heo <tj@kernel.org>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Byungchul Park <byungchul.park@lge.com>,
vlevenetz@mm-sol.com,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v10 1/2] printk: Make printk() completely async
Date: Thu, 18 Aug 2016 18:51:44 +0900 [thread overview]
Message-ID: <20160818095144.GA425@swordfish> (raw)
In-Reply-To: <20160818093329.GL13300@pathway.suse.cz>
On (08/18/16 11:33), Petr Mladek wrote:
[..]
> > > 2. Force synchronous printk inside WARN()/BUG() macros.
> >
> > will it help? semaphore up() calls wake_up_process() regardless the context.
> > not to mention that we still may have spin_dump() enabled.
>
> Good point. That changes my preferences :-)
>
> >
> > > 3. Force printk_deferred() inside WARN()/BUG() macros via the per-CPU
> > > printk_func.
> > >
> > > It might be elegant. But we do not want this outside the scheduler
> > > code. Therefore we would need special variants of WARN_*_SCHED()
> > > BUG_*_SCHED() macros.
>
> Also we need to make sure that everything will be done on a single CPU
> as the printk_func is per-CPU variable.
lib/dump_stack.c dump_stack() disables local IRQs, so we will stay
on the same CPU.
schematically dump_stack_deferred() looks like the one below. I don't
dump registers, that will require one more *_deferred() function.
and as you can see I've replaced show_stack() with save_stack_trace().
it's not entirely universal (as of now), but worked for my needs at
that time.
---
asmlinkage __visible void dump_stack_deferred(void)
{
unsigned long flags;
unsigned long stack_trace[16];
int was_locked;
int old, cpu;
int i;
struct stack_trace trace = {
.nr_entries = 0,
.max_entries = ARRAY_SIZE(stack_trace),
.entries = stack_trace,
.skip = 0,
};
local_irq_save(flags);
retry:
cpu = smp_processor_id();
old = atomic_cmpxchg(&dump_lock, -1, cpu);
if (old == -1) {
was_locked = 0;
} else if (old == cpu) {
was_locked = 1;
} else {
cpu_relax();
goto retry;
}
save_stack_trace(&trace);
for (i = 0; i < trace.nr_entries; i++) {
printk_deferred("[%p] %pS\n",
(void *)stack_trace[i],
(void *)stack_trace[i]);
}
if (!was_locked)
atomic_set(&dump_lock, -1);
local_irq_restore(flags);
}
---
-ss
next prev parent reply other threads:[~2016-08-18 9:51 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-04 16:57 [PATCH v10 0/2] printk: Make printk() completely async Sergey Senozhatsky
2016-04-04 16:57 ` [PATCH v10 1/2] " Sergey Senozhatsky
2016-04-04 22:51 ` Andrew Morton
2016-04-05 5:17 ` Sergey Senozhatsky
2016-04-05 7:39 ` Sergey Senozhatsky
2016-04-06 0:19 ` Sergey Senozhatsky
2016-04-06 8:27 ` Jan Kara
2016-04-07 9:48 ` Sergey Senozhatsky
2016-04-07 12:08 ` Sergey Senozhatsky
2016-04-07 13:15 ` Jan Kara
2016-08-10 21:17 ` Viresh Kumar
2016-08-12 9:44 ` Petr Mladek
2016-08-15 14:26 ` Vladislav Levenetz
2016-08-16 9:04 ` Petr Mladek
2016-08-18 2:27 ` Sergey Senozhatsky
2016-08-18 9:33 ` Petr Mladek
2016-08-18 9:51 ` Sergey Senozhatsky [this message]
2016-08-18 10:56 ` Petr Mladek
2016-08-19 6:32 ` Sergey Senozhatsky
2016-08-19 9:54 ` Petr Mladek
2016-08-19 19:00 ` Jan Kara
2016-08-20 5:24 ` Sergey Senozhatsky
2016-08-22 4:15 ` Sergey Senozhatsky
2016-08-23 12:19 ` Petr Mladek
2016-08-24 1:33 ` Sergey Senozhatsky
2016-08-25 21:10 ` Petr Mladek
2016-08-26 1:56 ` Sergey Senozhatsky
2016-08-26 8:20 ` Sergey Senozhatsky
2016-08-30 9:29 ` Petr Mladek
2016-08-31 2:31 ` Sergey Senozhatsky
2016-08-31 9:38 ` Petr Mladek
2016-08-31 12:52 ` Sergey Senozhatsky
2016-09-01 8:58 ` Petr Mladek
2016-09-02 7:58 ` Sergey Senozhatsky
2016-09-02 15:15 ` Petr Mladek
2016-09-06 7:16 ` Sergey Senozhatsky
2016-08-23 13:03 ` Petr Mladek
2016-08-23 13:48 ` Petr Mladek
2016-04-04 16:57 ` [PATCH v10 2/2] printk: Make wake_up_klogd_work_func() async Sergey Senozhatsky
2016-08-23 3:32 [PATCH v10 1/2] printk: Make printk() completely async Andreas Mohr
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