From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.osdl.org (smtp.osdl.org [65.172.181.4]) (using TLSv1 with cipher EDH-RSA-DES-CBC3-SHA (168/168 bits)) (Client CN "smtp.osdl.org", Issuer "OSDL Hostmaster" (not verified)) by ozlabs.org (Postfix) with ESMTP id 5597A67A5B for ; Thu, 25 May 2006 14:59:53 +1000 (EST) Date: Wed, 24 May 2006 21:59:17 -0700 From: Andrew Morton To: Benjamin Herrenschmidt Subject: Re: [Fwd: Re: via-pmu runs device_power_down in atomic context] Message-Id: <20060524215917.230af218.akpm@osdl.org> In-Reply-To: <1148531830.13249.237.camel@localhost.localdomain> References: <1148531830.13249.237.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: linuxppc-dev@ozlabs.org, Johannes Berg , Alan Stern , cpufreq@lists.linux.org.uk List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Benjamin Herrenschmidt wrote: > > -------- Forwarded Message -------- > From: Benjamin Herrenschmidt > To: Johannes Berg > Cc: linuxppc-dev list , Michael Hanselmann > , cpufreq@lists.linux.org.uk > Subject: Re: via-pmu runs device_power_down in atomic context > Date: Thu, 25 May 2006 12:28:15 +1000 > > On Wed, 2006-05-24 at 10:01 +0200, Johannes Berg wrote: > > Hey, > > > > Everytime I suspend my powerbook, I see the following trace: > > > > [10655.887546] BUG: sleeping function called from invalid context at include/linux/rwsem.h:43 > > [10655.887558] in_atomic():0, irqs_disabled():1 > > [10655.887562] Call Trace: > > [10655.887565] [C581BD20] [C00081E8] show_stack+0x50/0x190 (unreliable) > > [10655.887582] [C581BD50] [C0023BB0] __might_sleep+0xcc/0xe8 > > [10655.887592] [C581BD60] [C0038290] blocking_notifier_call_chain+0x2c/0xc0 > > [10655.887606] [C581BD80] [C01E90C0] cpufreq_suspend+0x130/0x148 > > [10655.887616] [C581BDB0] [C019D9E8] sysdev_suspend+0x10c/0x300 > > [10655.887627] [C581BDF0] [C01A3888] device_power_down+0x74/0xac > > [10655.887636] [C581BE10] [C01B1264] pmac_suspend_devices+0x98/0x188 > > [10655.887643] [C581BE30] [C01B18F0] pmu_ioctl+0x59c/0xbc0 > > [10655.887649] [C581BED0] [C008E898] do_ioctl+0x80/0x84 > > [10655.887660] [C581BEE0] [C008E928] vfs_ioctl+0x8c/0x48c > > [10655.887666] [C581BF10] [C008ED68] sys_ioctl+0x40/0x74 > > [10655.887673] [C581BF40] [C000F3A4] ret_from_syscall+0x0/0x38 > > > > The might_sleep() comes from down_read() and this happens because > > blocking_notifier_call_chain calls it, it is also commented to run in > > process context so this is all proper. > > device_power_down should be called with interrupts off, thus the PMU > driver is fine. It's a misnamed function, it calls the sysdev's suspend > and those should be called with irq off. I think the problem is more due > to some cpufreq or notifier change that somebody done to recent kernels > and that added some might_sleep.... I wonder why. > > Andrew, what's up there ? What is this new > "blocking_notifier_call_chain" thing ? notifiers use to not use > semaphores and not be blocking... at least powermac implementation of > cpufreq relies on that. notifiers used to be racy too - we just waddled across them without any locking. Alan made a best-effort conversion of callers, and there have been a few problems. Here, pmac has gone and unilaterally decided that device_power_down() is atomic, even though device_power_down() _already_ calls suspend_device(), which does down(). So I'd say you've gone and found a via-pmu bug here. A way of shutting up the warning would be to use an atomic notifier, but it'll still be buggy. Better would be to teach pmac_suspend_devices() not to assume things which aren't true ;)