linux-kernel - Re: [PATCH v2] locking/rwbase: Prevent indefinite writer starvation

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Date:   Fri, 20 Jan 2023 14:07:15 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Linux-RT <linux-rt-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] locking/rwbase: Prevent indefinite writer starvation

On Fri, Jan 20, 2023 at 02:38:27PM +0100, Sebastian Andrzej Siewior wrote:
> On 2023-01-20 13:24:41 [+0000], Mel Gorman wrote:
> > --- a/kernel/locking/rwbase_rt.c
> > +++ b/kernel/locking/rwbase_rt.c
> > @@ -264,12 +291,17 @@ static int __sched rwbase_write_lock(struct rwbase_rt *rwb,
> >  		if (__rwbase_write_trylock(rwb))
> >  			break;
> >  
> > +		/* Record timeout when reader bias is ignored. */
> > +		rwb->waiter_timeout = jiffies + RWBASE_RT_WAIT_TIMEOUT;
> 		rwb->waiter_timeout = (jiffies + RWBASE_RT_WAIT_TIMEOUT) | 1;
> 
> There is the unlikely case that (jiffies + RWBASE_RT_WAIT_TIMEOUT) = 0
> on 32bit where it is not jiffies64.
> 
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> 

Thanks very much, updated version will be posted shortly.

-- 
Mel Gorman
SUSE Labs