Subject: RT and Signals
From: Daniel Walker <dwalker@mvista.com>
Reply-To: dwalker@mvista.com
To: linux-kernel@vger.kernel.org
Cc: mingo@elte.hu
Content-Type: text/plain
Organization: MontaVista
Message-Id: <1113239666.30549.37.camel@dhcp153.mvista.com>
Mime-Version: 1.0
Date: 11 Apr 2005 10:14:27 -0700
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1087
Lines: 24


	I'm not sure if this has changed at all in recent RT patches, but I've
noticed several issues popping up that are related to the timer
interrupt sending signals , one in particular is the fact that
send_sig() calls into __cache_alloc() which has it's interrupt disable
protections removed in RT . I've observed slab corruption due to this
while running lmbench and LTP .

	Another issue was a livelock related to the timer interrupt calling
send_sig which locks tasklist_lock and siglock , which are both mutexes
(deadlock detect was on , but didn't trigger).. 

	LTP and lmbench seem to bring all these issues to the surface, but they
are all different depending on the architecture. I've been treating the
symptoms , but not the disease .. Ultimately , we need some protections,
in signal deliver, to stop the timer interrupt .. 

Daniel

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/