linux-kernel - Re: Re: [PATCH] futex: bugfix for robust futex deadlock when waking only one thread in handle_futex

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Date:	Fri, 19 Apr 2013 15:03:37 +0800
From:	zhang.yi20@....com.cn
To:	Darren Hart <dvhart@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Re: [PATCH] futex: bugfix for robust futex deadlock when waking only
 one thread in handle_futex_death

Darren Hart <dvhart@...ux.intel.com> wrote on 2013/04/18 22:54:30:

> 
> "or it will exit later" .... I don't follow you there, it sounds like
> you are saying if we try to wake the exiting process, that process will
> be delayed and take longer to exit.... I don't think that is what you
> meant. Can you elaborate please?
> 

I want to describe this scene:
1, We wake one waiter of other process that is not exiting.
2, Before it returns from do_futex, another thread of the process 
  encounters an exception and leads to process exiting.
3, The waiter returns from do_futex, and handle exit signal first, 
  that it will not return to userspace any more.

So, to my way of thinking, to choose a suitable waiter is difficult.

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