Messages in this thread | | | Date | Thu, 25 Aug 2011 13:14:16 +0100 | From | Russell King - ARM Linux <> | Subject | Re: try_to_freeze() called with IRQs disabled on ARM |
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On Wed, Aug 24, 2011 at 12:17:03AM +0200, Tejun Heo wrote: > On Wed, Aug 24, 2011 at 12:13 AM, Russell King - ARM Linux > <linux@arm.linux.org.uk> wrote: > > Thereby entirely preventing threads from being frozen? You're asking > > me to effectively disable suspend/resume on an architecture where it's > > heavily used. That's not a good idea, and would be an out-right > > regression. > > Eh? So, it's supposed to enter refrigerator with IRQ disabled? Then, > moving might_sleep() inside refrigerator() doesn't help either, does > it? Then we should be doing is, > > if (freezing() && IRQ disabled) { > bust on IRQ; > try_to_freeze(); > replug IRQ; > } > > But, that can't be right. The current code isn't triggering warning > from scheduler code, right? If the above is the case, it should be > triggering that. What am I missing?
The scheduler code does not check for CPU IRQs being masked. It just checks the preempt count, nothing more.
might_sleep() on the other hand checks the preempt count _and_ CPU IRQ mask state.
Note that your 'IRQ disabled' will always be true for ARM at this point at the moment - and conditionalizing this won't help (see below).
Given that get_signal_to_deliver() already forcefully enables IRQs, I think our syscall restarting is already horribly racy here in the way I've previously described.
It also looks to me like get_signal_to_deliver() already handles the freezing stuff, so does ARM even need this call here? Maybe when:
commit fc558a7496bfab3d29a68953b07a95883fdcfbb1 Author: Rafael J. Wysocki <rjw@sisk.pl> Date: Thu Mar 23 03:00:05 2006 -0800
[PATCH] swsusp: finally solve mysqld problem
was introduced, every other architecture should have been updated for that change... So this call in the ARM signal handling code to try_to_freeze() should just be deleted as it should've been done five years ago. -- 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/
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