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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: John Ogness <john.ogness@linutronix.de>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org
Subject: Re: consoles: was: [PATCH next v2 3/3] printk: remove logbuf_lock, add syslog_lock
Date: Sat, 5 Dec 2020 13:39:53 +0900	[thread overview]
Message-ID: <X8sPGfe2kWkAqsl1@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <X8phf/jITFd7nV38@alley>

On (20/12/04 17:19), Petr Mladek wrote:
[..]
> > --- a/kernel/printk/printk.c
> > +++ b/kernel/printk/printk.c
> > @@ -2432,7 +2490,6 @@ void console_unlock(void)
> >  		size_t len;
> >  
> >  		printk_safe_enter_irqsave(flags);
> 
> Why do we actually need to use the printk_safe context here?
> There is not longer a risk of deadlock caused by logbuf_lock.
> All other recursions should be prevented by console_trylock()
> in printk().

All semaphore functions, including down_trylock(), acquire
semaphore spin_lock; and then some call into the scheduler
(or other kernel core functions) under semaphore's spin_lock.
For instance

	up()
	 raw_spin_lock_irqsave(&sem->lock)
	   __up()
	     wake_up_process()
	       try_to_wake_up()

	-ss

  reply	other threads:[~2020-12-05  4:41 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-01 20:53 [PATCH next v2 0/3] printk: remove logbuf_lock John Ogness
2020-12-01 20:53 ` [PATCH next v2 1/3] printk: inline log_output(),log_store() in vprintk_store() John Ogness
2020-12-03 15:57   ` Petr Mladek
2020-12-03 16:25     ` John Ogness
2020-12-04  6:13       ` Sergey Senozhatsky
2020-12-04  8:26       ` Petr Mladek
2020-12-01 20:53 ` [PATCH next v2 2/3] printk: change @clear_seq to atomic64_t John Ogness
2020-12-04  9:12   ` Petr Mladek
2020-12-06 20:23     ` John Ogness
2020-12-07  9:34       ` Peter Zijlstra
2020-12-07 10:03         ` John Ogness
2020-12-07 12:56           ` Peter Zijlstra
2020-12-07 12:56           ` Petr Mladek
2020-12-07 16:46           ` David Laight
2020-12-08 20:34     ` Sergey Senozhatsky
2020-12-08 22:30       ` John Ogness
2020-12-09  1:04         ` Sergey Senozhatsky
2020-12-09  8:16         ` Peter Zijlstra
2020-12-09  9:22           ` Sergey Senozhatsky
2020-12-09 10:46             ` Sergey Senozhatsky
2020-12-09 11:00               ` Peter Zijlstra
2020-12-09 11:28                 ` Sergey Senozhatsky
2020-12-09 12:29                   ` Peter Zijlstra
2020-12-09  8:07       ` Peter Zijlstra
2020-12-01 20:53 ` [PATCH next v2 3/3] printk: remove logbuf_lock, add syslog_lock John Ogness
2020-12-04  6:41   ` Sergey Senozhatsky
2020-12-06 20:44     ` John Ogness
2020-12-04 15:52   ` devkmsg: was " Petr Mladek
2020-12-06 20:51     ` John Ogness
2020-12-07  9:56       ` Petr Mladek
2020-12-04 15:57   ` syslog: was: " Petr Mladek
2020-12-06 21:06     ` John Ogness
2020-12-07 10:01       ` Petr Mladek
2020-12-04 16:10   ` recursion handling: " Petr Mladek
2020-12-05  4:25     ` Sergey Senozhatsky
2020-12-06 22:08       ` John Ogness
2020-12-05  9:41     ` Sergey Senozhatsky
2020-12-06 22:17       ` John Ogness
2020-12-06 21:44     ` John Ogness
2020-12-07 11:17       ` Petr Mladek
2020-12-04 16:15   ` vprintk_store: was: " Petr Mladek
2020-12-06 22:30     ` John Ogness
2020-12-07 12:46       ` Petr Mladek
2020-12-04 16:19   ` consoles: " Petr Mladek
2020-12-05  4:39     ` Sergey Senozhatsky [this message]
2020-12-07  9:50       ` Petr Mladek
2020-12-08 20:51         ` Sergey Senozhatsky

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