From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Teddy Astie <teddy.astie@vates.tech>,
Nicola Vetrini <nicola.vetrini@bugseng.com>
Subject: Re: [PATCH] x86/time: make do_settime() uses more accurate
Date: Thu, 7 May 2026 12:26:51 +0200 [thread overview]
Message-ID: <afxo63Wy9en59pmO@macbook.local> (raw)
In-Reply-To: <99a4a514-3ed5-43f7-823c-54771f3bd03d@suse.com>
On Wed, May 06, 2026 at 11:35:45AM +0200, Jan Beulich wrote:
> As a comment next to one of the invocations states, get_wallclock_time()
> can take over a second. The order of evaluation of function arguments is
> in principle unspecified; in practice at least gcc looks to be evaluating
> them from last to first. Hence with NOW() invoked first, the respective
> value passed to do_settime() can be off by over a second (which is in
> contrast to __get_cmos_time() attempting to get the time exactly after an
> update, i.e. [pretty] precisely at a seconds boundary).
>
> This also addresses a Misra C:2012 rule 13.2 ("The value of an expression
> and its persistent side-effects shall be the same under all permitted
> evaluation orders") violation each.
>
> Fixes: f64134cdb81c ("x86: Fix time_resume() to notify all domains of wallclock change")
> Fixes: 0bfcf984b727 ("x86: Reintroduce clocksource=tsc")
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Thanks, Roger.
prev parent reply other threads:[~2026-05-07 10:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-06 9:35 [PATCH] x86/time: make do_settime() uses more accurate Jan Beulich
2026-05-06 9:47 ` Andrew Cooper
2026-05-06 9:48 ` Andrew Cooper
2026-05-06 9:53 ` Nicola Vetrini
2026-05-06 11:15 ` Roger Pau Monné
2026-05-06 11:45 ` Jan Beulich
2026-05-06 12:49 ` Roger Pau Monné
2026-05-07 10:26 ` Roger Pau Monné [this message]
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