linux-kernel - Re: [LTP] [patch V2 00/20] timer: Refactor the timer wheel

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Message-ID: <alpine.DEB.2.11.1606231720080.5839@nanos>
Date:	Thu, 23 Jun 2016 17:21:14 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Cyril Hrubis <chrubis@...e.cz>
cc:	George Spelvin <linux@...encehorizons.net>, arjan@...radead.org,
	clm@...com, edumazet@...gle.com, fweisbec@...il.com,
	lenb@...nel.org, linux-kernel@...r.kernel.org, ltp@...ts.linux.it,
	mingo@...nel.org, paulmck@...ux.vnet.ibm.com, peterz@...radead.org,
	riel@...hat.com, rt@...utronix.de, torvalds@...ux-foundation.org,
	umgwanakikbuti@...il.com
Subject: Re: [LTP] [patch V2 00/20] timer: Refactor the timer wheel

On Thu, 23 Jun 2016, Cyril Hrubis wrote:
> > 1) sigtimedwait() is unusual in that it uses the jiffies timer.  Most
> >    system call timeouts (including specifically the one in FUTEX_WAIT)
> >    use the high-resolution timer subsystem, which is a whole different
> >    animal with tighter guarantees, and
> 
> That is likely POSIX conformance bug, since POSIX explicitly states that
> sigtimedwait() shall use CLOCK_MONOTONIC to measure the timeout.
> 
> "If the Monotonic Clock option is supported, the CLOCK_MONOTONIC clock
> shall be used to measure the time interval specified by the timeout
> argument."

That's fine because jiffies is a less granular form of CLOCK_MONOTONIC.
 
Thanks,

	tglx