linux-kernel - RE: [KERNEL BUG] do_timer/tick_handover_do

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Message-ID: <5C6899BCED92C94EBDCC00F80838E3D52113A944@SJEXCHMB06.corp.ad.broadcom.com>
Date:	Thu, 7 May 2015 08:47:14 +0000
From:	"Oza (Pawandeep) Oza" <oza@...adcom.com>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
CC:	pawandeep oza <oza.contri.linux.kernel@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	malayasen rout <malayasen.rout@...il.com>
Subject: RE: [KERNEL BUG] do_timer/tick_handover_do_timer 3.10.17

Oh ok.
So the reason why I cared was:

There is a code in our base which relies on jiffies, but since jiffies are not incrementing, the code waits there and loops forever.
And forward progress is on halt. (on cpu0, since that is the only cpu, which is alive)

We have changed the code to use mdelay and things move on.

But that means that in the patch which I mentioned, 
any code which relies on jiffies will stuck forever and will not allow rest of the code to get executed and hence no forward progress.
specially if that code is running with preempt_disable();

Regards,
-Oza

-----Original Message-----
From: Mike Galbraith [mailto:umgwanakikbuti@...il.com] 
Sent: Thursday, May 07, 2015 2:00 PM
To: Oza (Pawandeep) Oza
Cc: pawandeep oza; linux-kernel@...r.kernel.org; malayasen rout
Subject: Re: [KERNEL BUG] do_timer/tick_handover_do_timer 3.10.17

On Thu, 2015-05-07 at 07:05 +0000, Oza (Pawandeep) Oza wrote:
> : )
> 
> Well, I am not sure, if problem was communicated clearly from my side.

I understood.  I just don't understand why you'd care deeply whether
CPU0 halts or eternally waits.  Both render it harmless and useless.

	-Mike