linux-kernel - RE: [PATCH] locking/rwsem: Fix kernel crash when spinning on RWSEM_OWNER

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Message-ID: <8930570b92aa435b941c99dff00c7802@AcuMS.aculab.com>
Date:   Wed, 15 Jan 2020 16:01:28 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Waiman Long' <longman@...hat.com>, Christoph Hellwig <hch@....de>
CC:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH] locking/rwsem: Fix kernel crash when spinning on
 RWSEM_OWNER_UNKNOWN

From: Waiman Long
> Sent: 15 January 2020 15:48
...
> It depends. I find it hard to read an expression with "&" and "&&"
> without parentheses. Anyway, I will admit that the above code is
> inconsistent in term of how parentheses are used. So I will change that.

Conditionals containing fragments like (a == b && c == d && ...)
are much easier to read without any extra ().

The only problem with && is that when K&R added it to C they didn't
change the priority of & to be higher than == (where it should be).
At that time they could have changed all the existing code...
Modern compilers do warn about (a == b & c).

	David

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