From: Peter Zijlstra <peterz@infradead.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Kees Cook <keescook@chromium.org>, Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 00/19] Enable -Wshadow=local for kernel/sched
Date: Wed, 2 Mar 2022 20:18:06 +0100 [thread overview]
Message-ID: <Yh/C7nnElPOL3G/k@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <Yh+67VF0/OFSp15y@casper.infradead.org>
On Wed, Mar 02, 2022 at 06:43:57PM +0000, Matthew Wilcox wrote:
> ie "__ret = freezable_schedule_timeout(__ret)" is supposed to refer to
> the inner __ret, not the outer __ret. Which was the opposite of what
> I thought was supposed to happen.
>
> We can fix this, of course. Something like ...
>
> #define ___wait_event_freezable_timeout(wq_head, condition, timeout, ret) \
> ___wait_event(wq_head, ___wait_cond_timeout(condition, ret), \
> TASK_INTERRUPTIBLE, 0, timeout, \
> ret = freezable_schedule_timeout(ret), ret)
>
> #define __wait_event_freezable_timeout(wq_head, condition, timeout) \
> ___wait_event_freezable_timeout(wq_head, condition, timeout, UNIQUE_ID)
>
> ... and now all the 'ret' refer to the thing that they look like they're
> referring to.
Right; so the trick is to make sure all ___wait_event() users will have
a ret and then the inner ret can go away. The interruptible/timeout
variants all already have a ret variable, but the unconditional things
like wait_event() do not (which is where all the trouble started).
By simply adding a ret variable, even to the variants without return
value, the inner variable can go away and the shadowing goes away.
next prev parent reply other threads:[~2022-03-02 19:18 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-02 4:34 Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 01/19] wait: Parameterize the return variable to ___wait_event() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 02/19] swait: Parameterize the return variable to __swait_event_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 03/19] swait: Parameterize the return variable to __swait_event_interruptible_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 04/19] swait: Parameterize the return variable to __swait_event_idle_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 05/19] wait: Parameterize the return variable to __wait_event_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 06/19] wait: Parameterize the return variable to __wait_event_freezable_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 07/19] wait: Parameterize the return variable to __wait_event_interruptible_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 08/19] wait: Parameterize the return variable to __wait_event_idle_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 09/19] wait: Parameterize the return variable to __wait_event_idle_exclusive_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 10/19] wait: Parameterize the return variable to __wait_event_killable_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 11/19] wait: Parameterize the return variable to __wait_event_lock_irq_timeout() Matthew Wilcox (Oracle)
2022-03-02 4:34 ` [PATCH 12/19] wait_bit: Parameterize the return variable to __wait_var_event_timeout() Matthew Wilcox (Oracle)
2022-03-02 18:32 ` [PATCH 00/19] Enable -Wshadow=local for kernel/sched Kees Cook
2022-03-02 18:43 ` Matthew Wilcox
2022-03-02 19:18 ` Peter Zijlstra [this message]
2024-04-16 21:15 ` Kees Cook
2024-04-17 0:29 ` Linus Torvalds
2024-04-17 0:50 ` Linus Torvalds
2024-04-17 0:52 ` Matthew Wilcox
2024-04-17 11:23 ` Ingo Molnar
2024-04-19 22:06 ` Kees Cook
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