Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755406AbZKMJAb (ORCPT ); Fri, 13 Nov 2009 04:00:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755002AbZKMJA1 (ORCPT ); Fri, 13 Nov 2009 04:00:27 -0500 Received: from e23smtp09.au.ibm.com ([202.81.31.142]:51310 "EHLO e23smtp09.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754882AbZKMJA0 (ORCPT ); Fri, 13 Nov 2009 04:00:26 -0500 Message-ID: <4AFD2027.5060303@in.ibm.com> Date: Fri, 13 Nov 2009 14:30:23 +0530 From: Sachin Sant User-Agent: Thunderbird 2.0.0.22 (X11/20090609) MIME-Version: 1.0 To: Peter Zijlstra CC: LKML , Stephen Rothwell , linux-next@vger.kernel.org, Ingo Molnar , Mike Galbraith , Gautham R Shenoy Subject: Re: -next: Nov 12 - kernel BUG at kernel/sched.c:7359! References: <20091112195101.63263490.sfr@canb.auug.org.au> <4AFBF73B.5040500@in.ibm.com> <1258027820.4039.129.camel@laptop> <4AFBFE3D.80507@in.ibm.com> <1258028831.4039.152.camel@laptop> <1258045831.4039.736.camel@laptop> In-Reply-To: <1258045831.4039.736.camel@laptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3963 Lines: 100 Peter Zijlstra wrote: > So what we need to do is make the whole of select_task_rq_fair() > cpu_online/active_mask aware, or give up and simply punt: > > diff --git a/kernel/sched.c b/kernel/sched.c > index 1f2e99d..62df61c 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -2377,6 +2377,9 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, > task_rq_unlock(rq, &flags); > > cpu = p->sched_class->select_task_rq(p, SD_BALANCE_WAKE, wake_flags); > + if (!cpu_active(cpu)) > + cpu = cpumask_any_and(&p->cpus_allowed, cpu_active_mask); > + > if (cpu != orig_cpu) { > local_irq_save(flags); > rq = cpu_rq(cpu); > > > Something I think Mike also tried and didn't deadlock for him.. > > Sachin, Mike, could you try the above snippet and verify if it does > indeed solve your respective issues? > Unfortunately the above patch made things worse. With this patch the machine failed to boot with following oops CPU0: Dual-Core AMD Opteron(tm) Processor 2218 stepping 02 BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 IP: [] set_task_cpu+0x189/0x1ed PGD 0 Oops: 0000 [#1] SMP last sysfs file: CPU 0 Modules linked in: Pid: 3, comm: kthreadd Not tainted 2.6.32-rc7-next-20091113 #1 BladeCenter LS21 -[79716AA]- RIP: 0010:[] [] set_task_cpu+0x189/0x1ed RSP: 0018:ffff88012b357dd0 EFLAGS: 00010046 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000004 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff88012b340000 RBP: ffff88012b357e10 R08: 0000000000000004 R09: ffff88012b3401f8 R10: 00000000000cffa7 R11: 0000000000000000 R12: ffff88012b340000 R13: 000000000c28ccf6 R14: 0000000000000004 R15: ffff880028214cc0 FS: 0000000000000000(0000) GS:ffff880028200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b CR2: 0000000000000020 CR3: 000000000174e000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process kthreadd (pid: 3, threadinfo ffff88012b356000, task ffff88012b3431c0) Stack: ffff880028214d20 0000000000000000 0000000028215640 0000000000000000 <0> ffff88012b340000 0000000000000001 ffff880028214cc0 0000000000000000 <0> ffff88012b357e60 ffffffff81063a75 0000000000000000 0000000000000000 Call Trace: [] try_to_wake_up+0x103/0x31f [] default_wake_function+0xd/0xf [] __wake_up_common+0x46/0x76 [] ? migration_thread+0x0/0x285 [] complete+0x38/0x4b [] kthread+0x67/0x85 [] child_rip+0xa/0x20 [] ? kthread+0x0/0x85 [] ? child_rip+0x0/0x20 Code: 00 8b 05 dd d7 df 04 85 c0 74 19 45 31 c0 31 c9 ba 01 00 00 00 be 01 00 00 00 bf 04 00 00 00 e8 79 02 07 00 48 8b 55 c8 44 89 f1 <48> 8b 42 20 48 8b 55 c0 49 03 84 24 88 00 00 00 48 2b 42 20 49 RIP [] set_task_cpu+0x189/0x1ed RSP CR2: 0000000000000020 ---[ end trace 4eaa2a86a8e2da22 ]--- I tried this with today's next (2.6.32-rc7-20091113) + the above patch. Here is how the code looks after applying the patch... task_rq_unlock(rq, &flags); cpu = p->sched_class->select_task_rq(p, SD_BALANCE_WAKE, wake_flags); if (!cpu_active(cpu)) cpu = cpumask_any_and(&p->cpus_allowed, cpu_active_mask); if (cpu != orig_cpu) set_task_cpu(p, cpu); Thanks -Sachin -- --------------------------------- Sachin Sant IBM Linux Technology Center India Systems and Technology Labs Bangalore, India --------------------------------- -- 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/