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Date: Mon, 16 Jan 2017 22:43:28 +0900 From: Sergey Senozhatsky <sergey.senozhatsky@...il.com> To: Sergey Senozhatsky <sergey.senozhatsky@...il.com> Cc: Petr Mladek <pmladek@...e.com>, Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>, Steven Rostedt <rostedt@...dmis.org>, Peter Zijlstra <peterz@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jslaby@...e.cz>, linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] printk: Correctly handle preemption in console_unlock() On (01/16/17 22:26), Sergey Senozhatsky wrote: > On (01/16/17 13:48), Petr Mladek wrote: > [..] > > The async printk code looks like this: > > > > vprintk_emit(...) > > { > > > > > > if (can_printk_async()) { > > /* Offload printing to a schedulable context. */ > > printk_kthread_need_flush_console = true; > > wake_up_process(printk_kthread); > > } else { > > /* > > * Try to acquire and then immediately release the > > * console semaphore. The release will print out > > * buffers and wake up /dev/kmsg and syslog() users. > > */ > > if (console_trylock()) > > console_unlock(); > > } > > > > So, there is still the console_trylock() for the sync mode. Or do I > > see an outdated variant? > > no, it doesn't. I meant that none of this is happening in vprintk_emit(). there is no console_sem in vprintk_emit() at all. eveything is done in deferred printk. -ss
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