From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 5AD7567A41 for ; Thu, 25 May 2006 12:30:45 +1000 (EST) Subject: Re: via-pmu runs device_power_down in atomic context From: Benjamin Herrenschmidt To: Johannes Berg In-Reply-To: <1148457661.11734.9.camel@johannes> References: <1148457661.11734.9.camel@johannes> Content-Type: text/plain Date: Thu, 25 May 2006 12:28:15 +1000 Message-Id: <1148524096.13249.119.camel@localhost.localdomain> Mime-Version: 1.0 Cc: linuxppc-dev list , cpufreq@lists.linux.org.uk List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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. > However, it obviously isn't run at process context. Looking why, I see > this in via-pmu.c: > /* We can now disable MSR_EE. This code of course works properly only > * on UP machines... For SMP, if we ever implement sleep, we'll have to > * stop the "other" CPUs way before we do all that stuff. > */ > local_irq_disable(); > > /* Broadcast power down irq > * This isn't that useful in most cases (only directly wired devices can > * use this but still... This will take care of sysdev's as well, so > * we exit from here with local irqs disabled and PIC off. > */ > ret = device_power_down(PMSG_SUSPEND); > > Apparently this was a deliberate decision. > > So the question is: which is correct? I can test and submit a patch to > fix the issue at either end; if cpufreq is wrong I'd move from a > blocking_ to an atomic_notifier_call_chain, if via-pmu.c is wrong I'd > call device_power_down earlier... > > johannes