From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Thu, 08 May 2008 22:55:20 +0200
From: Philippe Gerum <rpm@xenomai.org>
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Sender: Philippe Gerum <philippe.gerum@domain.hid>
Subject: Re: [Adeos-main] [BUG] ipipe_sync_stage deadlock
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To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: adeos-main <adeos-main@gna.org>

Jan Kiszka wrote:
> I love KVM - not only because I'm heavily hacking on it now, also
> because it is so easy to trigger various kinds of guest issues with
> it (SMP host + threaded virtual CPUs => true SMP guest - and if you
> want to watch fancy things happen, just load one host core).
> 
> Here is one I found that way:
> 
> void fastcall __ipipe_sync_stage(unsigned long syncmask)
> {
> [ ... ]
> 	while ((mask = (ipipe_this_cpudom_var(irqpend_himask) & syncmask)) != 0) {
> 		level = __ipipe_ffnz(mask);
> 
> 		while ((submask = ipipe_this_cpudom_var(irqpend_lomask)[level]) != 0) {
> 			rank = __ipipe_ffnz(submask);
> 			irq = (level << IPIPE_IRQ_ISHIFT) + rank;
> 
> 			if (test_bit(IPIPE_LOCK_FLAG, &ipd->irqs[irq].control)) {
> 				__clear_bit(rank, &ipipe_this_cpudom_var(irqpend_lomask)[level]);
- 				continue;
+				goto rpm_needs_more_neurons;
> 			}
> 
> 			__clear_bit(rank, &ipipe_this_cpudom_var(irqpend_lomask)[level]);
> 
+ rpm_needs_more_neurons:
> 			if (ipipe_this_cpudom_var(irqpend_lomask)[level] == 0)
> 				__clear_bit(level, &ipipe_this_cpudom_var(irqpend_himask));
> [ ... ]
> 
> Who sees the deadlock? 100 points for the right answer! But be quick,
> I'm already hacking on a fix. :)
> 
> Jan
> 
> 
> 
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> 
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-- 
Philippe.