linux-kernel - Re: [PATCH v3 2/4] locking/rwsem: Don't wake up one's own task

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Message-ID: <573B58D4.4090406@hurleysoftware.com>
Date:	Tue, 17 May 2016 10:45:56 -0700
From:	Peter Hurley <peter@...leysoftware.com>
To:	Waiman Long <Waiman.Long@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Davidlohr Bueso <dave@...olabs.net>,
	Jason Low <jason.low2@...com>,
	Dave Chinner <david@...morbit.com>,
	Scott J Norton <scott.norton@....com>,
	Douglas Hatch <doug.hatch@....com>
Subject: Re: [PATCH v3 2/4] locking/rwsem: Don't wake up one's own task

On 05/12/2016 03:56 PM, Waiman Long wrote:
> As rwsem_down_read_failed() will queue itself and potentially call
> __rwsem_do_wake(sem, RWSEM_WAKE_ANY), it is possible that a reader
> will try to wake up its own task. This patch adds a check to make
> sure that this won't happen.

Although there's no particular harm in the current code, this at
least spells out this condition is normal (ie., when a failed reader
wakes itself while waking the other waiting readers).

Reviewed-by: Peter Hurley <peter@...leysoftware.com>