linux-kernel - Re: [GIT PULL] updates for oprofile

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Date:	Tue, 27 Apr 2010 20:47:51 +0300
From:	Siarhei Siamashka <siarhei.siamashka@...ia.com>
To:	oprofile-list@...ts.sourceforge.net
Cc:	ext Robert Richter <robert.richter@....com>,
	"Carmody Phil.2 (EXT-Ixonos/Helsinki)" <ext-phil.2.carmody@...ia.com>,
	"schwidefsky@...ibm.com" <schwidefsky@...ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] updates for oprofile

On Tuesday 27 April 2010 20:40:26 ext Robert Richter wrote:
> On 27.04.10 18:25:44, Phil Carmody wrote:
> > Now oprofile_add_sample() is called from this context:
> > """
> > static enum hrtimer_restart oprofile_hrtimer_notify(struct hrtimer
> > *hrtimer) {
> >          oprofile_add_sample(get_irq_regs(), 0);
> > """
> >
> > And get_irq_regs() is NULL when not in an IRQ context.
>
> Perf is simply dropping the sample in such cases, see:
>
>  kernel/perf_event.c:perf_swevent_hrtimer()
>
> So at quick fix would be to check for a null pointer also. But,
> according to this:
>
>  http://www.mail-archive.com/linux-omap@vger.kernel.org/msg14074.html
>
> samples will be incorrect then since only interrupt context is
> profiled. It seems there is no solution available right now.

Isn't hrtimer callback function supposed to be only called from IRQ context
after this cleanup: http://lwn.net/Articles/308545/ ?

-- 
Best regards,
Siarhei Siamashka
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