Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755159Ab0GIWdV (ORCPT ); Fri, 9 Jul 2010 18:33:21 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:59736 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753655Ab0GIWdU (ORCPT ); Fri, 9 Jul 2010 18:33:20 -0400 From: Darren Hart To: linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Eric Dumazet , John Kacur , Steven Rostedt , Mike Galbraith , linux-rt-users@vger.kernel.org Subject: [PATCH 0/4][RT] futex: fix tasks blocking on two rt_mutex locks Date: Fri, 9 Jul 2010 15:32:56 -0700 Message-Id: <1278714780-788-1-git-send-email-dvhltc@us.ibm.com> X-Mailer: git-send-email 1.7.0.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5325 Lines: 108 This patch-set address the following problem reported by Mike Galbraith: > Stress testing, looking to trigger RCU stalls, I've managed to find a > way to repeatably create fireworks. (got RCU stall, see attached) > > 1. download ltp-full-20100630. Needs to be this version because of > testcase bustage in earlier versions, and must be built with gcc > 4.3, > else testcases will segfault due to a gcc bug. > > 2. apply patchlet so you can run testcases/realtime/perf/latency/run.sh > at all. > > --- pthread_cond_many.c.org 2010-07-05 09:05:59.000000000 +0200 > +++ pthread_cond_many.c 2010-07-04 12:12:25.000000000 +0200 > @@ -259,7 +259,7 @@ void usage(void) > > int parse_args(int c, char *v) > { > - int handled; > + int handled = 1; > switch (c) { > case 'h': > usage(); > > 3. add --realtime for no particular reason. > > --- run.sh.org 2010-07-06 15:54:58.000000000 +0200 > +++ run.sh 2010-07-06 16:37:34.000000000 +0200 > @@ -22,7 +22,7 @@ make > # process to run realtime. The remainder of the processes (if any) > # will run non-realtime in any case. > > -nthread=5000 > +nthread=500 > iter=400 > nproc=5 > > @@ -39,7 +39,7 @@ i=0 > i=1 > while test $i -lt $nproc > do > - ./pthread_cond_many --broadcast -i $iter -n $nthread > $nthread.$iter.$nproc.$i.out & > + ./pthread_cond_many --realtime --broadcast -i $iter -n $nthread > $nthread.$iter.$nproc.$i.out & > i=`expr $i + 1` > done > wait The LTP wreckage will be addressed separately > 4. run it. > > What happens here is we hit WARN_ON(pendowner->pi_blocked_on != waiter), > this does not make it to consoles (poking sysrq-foo doesn't either). > Next comes WARN_ON(!pendowner->pi_blocked_on), followed by the NULL > explosion, which does make it to consoles. > > With explosion avoidance, I also see pendowner->pi_blocked_on->task == > NULL at times, but that, as !pendowner->pi_blocked_on, seems to be > fallout. The start of bad juju is always pi_blocked_on != waiter. > > [ 141.609268] BUG: unable to handle kernel NULL pointer dereference at 0000000000000058 > [ 141.609268] IP: [] wakeup_next_waiter+0x12c/0x177 > [ 141.609268] PGD 20e174067 PUD 20e253067 PMD 0 > [ 141.609268] Oops: 0000 [#1] PREEMPT SMP > [ 141.609268] last sysfs file: /sys/devices/system/cpu/cpu3/cache/index2/shared_cpu_map > [ 141.609268] CPU 0 > [ 141.609268] Pid: 8154, comm: pthread_cond_ma Tainted: G W 2.6.33.6-rt23 #12 MS-7502/MS-7502 > [ 141.609268] RIP: 0010:[] [] wakeup_next_waiter+0x12c/0x177 > [ 141.609268] RSP: 0018:ffff88020e3cdd78 EFLAGS: 00010097 > [ 141.609268] RAX: 0000000000000000 RBX: ffff8801e8eba5c0 RCX: 0000000000000000 > [ 141.609268] RDX: ffff880028200000 RSI: 0000000000000046 RDI: 0000000000000009 > [ 141.609268] RBP: ffff88020e3cdda8 R08: 0000000000000002 R09: 0000000000000000 > [ 141.609268] R10: 0000000000000005 R11: 0000000000000000 R12: ffffffff81659068 > [ 141.609268] R13: ffff8801e8ebdb58 R14: 0000000000000000 R15: ffff8801e8ebac08 > [ 141.609268] FS: 00007f664d539700(0000) GS:ffff880028200000(0000) knlGS:0000000000000000 > [ 141.609268] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 141.609268] CR2: 0000000000000058 CR3: 0000000214266000 CR4: 00000000000006f0 > [ 141.609268] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 141.609268] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > [ 141.609268] Process pthread_cond_ma (pid: 8154, threadinfo ffff88020e3cc000, task ffff88020e2a4700) > [ 141.609268] Stack: > [ 141.609268] 0000000000000000 ffffffff81659068 0000000000000202 0000000000000000 > [ 141.609268] <0> 0000000000000000 0000000080001fda ffff88020e3cddc8 ffffffff812fec48 > [ 141.609268] <0> ffffffff81659068 0000000000606300 ffff88020e3cddd8 ffffffff812ff1b9 > [ 141.609268] Call Trace: > [ 141.609268] [] rt_spin_lock_slowunlock+0x43/0x61 > [ 141.609268] [] rt_spin_unlock+0x46/0x48 > [ 141.609268] [] do_futex+0x83c/0x935 > [ 141.609268] [] ? handle_mm_fault+0x6de/0x6f1 > [ 141.609268] [] ? do_futex+0x8f3/0x935 > [ 141.609268] [] sys_futex+0x142/0x154 > [ 141.609268] [] ? do_page_fault+0x23e/0x28e > [ 141.609268] [] ? math_state_restore+0x3d/0x3f > [ 141.609268] [] ? do_device_not_available+0xe/0x12 > [ 141.609268] [] system_call_fastpath+0x16/0x1b > [ 141.609268] Code: c7 09 6d 41 81 e8 ac 34 fd ff 4c 39 ab 70 06 00 00 74 11 be 47 02 00 00 48 c7 c7 09 6d 41 81 e8 92 34 fd ff 48 8b 83 70 06 00 00 <4c> 39 60 58 74 11 be 48 02 00 00 48 c7 c7 09 6d 41 81 e8 74 34 > [ 141.609268] RIP [] wakeup_next_waiter+0x12c/0x177 > [ 141.609268] RSP > [ 141.609268] CR2: 0000000000000058 > [ 141.609268] ---[ end trace 58805b944e6f93ce ]--- > [ 141.609268] note: pthread_cond_ma[8154] exited with preempt_count 2 -- 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/