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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Tejun Heo <tj@kernel.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Steven Rostedt <rostedt@goodmis.org>,
	Petr Mladek <pmladek@suse.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	linux-kernel@vger.kernel.org
Subject: Re: printk() from NMI backtrace can delay a lot
Date: Wed, 4 Jul 2018 01:39:48 +0900	[thread overview]
Message-ID: <20180703163948.GD391@tigerII.localdomain> (raw)
In-Reply-To: <20180703163145.GB391@tigerII.localdomain>

On (07/04/18 01:31), Sergey Senozhatsky wrote:
> it might be the case that we can do
> 
> 	serial_driver_handle_irq()
> 	{
> 		spin_loc(uart_port->lock);
> 
> 		.. TX / RX
> 
> 		spin_unlock(uart_port->lock);
> 
> 		tty_flip_buffer_push(uart_port->tty_port);
> 	}
> 
> This should break this chain
> 
> 	uart_port->lock -> pool->lock   // -> sheduler/etc.
> 
> 
> Can we do it? What am I missing?

Hmm, and we actually have some serial drivers that do tty_filp_buffer_push()
outside of uart_port->lock. For instance, drivers/tty/serial/efm32-uart.c
irqreturn_t efm32_uart_rxirq().

	-ss

  reply	other threads:[~2018-07-03 16:39 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-02 10:26 Tetsuo Handa
2018-07-02 10:39 ` Sergey Senozhatsky
2018-07-03  4:30 ` Sergey Senozhatsky
2018-07-03 15:29   ` Tejun Heo
2018-07-03 16:31     ` Sergey Senozhatsky
2018-07-03 16:39       ` Sergey Senozhatsky [this message]
2018-07-10 11:50       ` Petr Mladek
2018-07-11  7:27         ` Sergey Senozhatsky

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