linux-kernel - Re: [PATCH v1] [semaphore] Removed redundant code from semaphore's down family of function

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Message-ID: <20190830104604.GC2369@hirez.programming.kicks-ass.net>
Date:   Fri, 30 Aug 2019 12:46:04 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Satendra Singh Thakur <sst2005@...il.com>
Cc:     satendrasingh.thakur@....com, tglx@...utronix.de,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] [semaphore] Removed redundant code from semaphore's
 down family of function

On Fri, Aug 30, 2019 at 04:10:10PM +0530, Satendra Singh Thakur wrote:

> > +static inline long schedule_timeout(long timeout)
> > +{
> > +	if (__builtin_constant_p(timeout) && timeout == MAX_SCHEDULE_TIMEOUT) {
> > +		schedule();
> > +		return timeout;
> > +	}
> > +
> > +	return __schedule_timeout(timeout);
> > +}

> > +	if (timeout == MAX_SCHEDULE_TIMEOUT) {
> > 		schedule();
> > -		goto out;
> Hi Mr Peter,
> I have a suggestion here:
> The condition timeout == MAX_SCHEDULE_TIMEOUT is already handled in
> schedule_timeout function

Only if it is a compile time constant; otherwise it will end up here.

> and  same conditon is handled again in __schedule_timeout.
> Currently, no other function calls __schedule_timeout except schedule_timeout.
> Therefore, it seems this condition will never become true.

Please read more careful.