Messages in this thread | | | Date | Sat, 29 Sep 2012 08:46:42 +0200 | From | Sasha Levin <> | Subject | Re: rcu: eqs related warnings in linux-next |
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On 09/28/2012 07:31 PM, Paul E. McKenney wrote: > On Fri, Sep 28, 2012 at 03:36:43PM +0200, Frederic Weisbecker wrote: >> > On Fri, Sep 28, 2012 at 02:51:03PM +0200, Sasha Levin wrote: >>> > > Hi all, >>> > > >>> > > While fuzzing with trinity inside a KVM tools guest with the latest linux-next kernel, I've stumbled on the following during boot: >>> > > >>> > > [ 199.224369] WARNING: at kernel/rcutree.c:513 rcu_eqs_exit_common+0x4a/0x3a0() >>> > > [ 199.225307] Pid: 1, comm: init Tainted: G W 3.6.0-rc7-next-20120928-sasha-00001-g8b2d05d-dirty #13 >>> > > [ 199.226611] Call Trace: >>> > > [ 199.226951] [<ffffffff811c8d1a>] ? rcu_eqs_exit_common+0x4a/0x3a0 >>> > > [ 199.227773] [<ffffffff81108e36>] warn_slowpath_common+0x86/0xb0 >>> > > [ 199.228572] [<ffffffff81108f25>] warn_slowpath_null+0x15/0x20 >>> > > [ 199.229348] [<ffffffff811c8d1a>] rcu_eqs_exit_common+0x4a/0x3a0 >>> > > [ 199.230037] [<ffffffff8117f267>] ? __lock_acquire+0x1c37/0x1ca0 >>> > > [ 199.230037] [<ffffffff811c936c>] rcu_eqs_exit+0x9c/0xb0 >>> > > [ 199.230037] [<ffffffff811c940c>] rcu_user_exit+0x8c/0xf0 >>> > > [ 199.230037] [<ffffffff810a98bb>] do_page_fault+0x1b/0x40 >>> > > [ 199.230037] [<ffffffff810a2a90>] do_async_page_fault+0x30/0xa0 >>> > > [ 199.230037] [<ffffffff83a3eea8>] async_page_fault+0x28/0x30 >>> > > [ 199.230037] [<ffffffff819f357b>] ? debug_object_activate+0x6b/0x1b0 >>> > > [ 199.230037] [<ffffffff819f3586>] ? debug_object_activate+0x76/0x1b0 >>> > > [ 199.230037] [<ffffffff8111af13>] ? lock_timer_base.isra.19+0x33/0x70 >>> > > [ 199.230037] [<ffffffff8111d45f>] mod_timer_pinned+0x9f/0x260 >>> > > [ 199.230037] [<ffffffff811c5ff4>] rcu_eqs_enter_common+0x894/0x970 >>> > > [ 199.230037] [<ffffffff839dc2ac>] ? init_post+0x75/0xc8 >>> > > [ 199.230037] [<ffffffff85abfed5>] ? kernel_init+0x1e1/0x1e1 >>> > > [ 199.230037] [<ffffffff811c63df>] rcu_eqs_enter+0xaf/0xc0 >>> > > [ 199.230037] [<ffffffff811c64c5>] rcu_user_enter+0xd5/0x140 >>> > > [ 199.230037] [<ffffffff8107d0fd>] syscall_trace_leave+0xfd/0x150 >>> > > [ 199.230037] [<ffffffff83a3f7af>] int_check_syscall_exit_work+0x34/0x3d >>> > > [ 199.230037] ---[ end trace a582c3a264d5bd1a ]--- >> > >> > Ok, we can't decently protect against any kind of exception messing up everything >> > in the middle of RCU APIs anyway. The only solution is to find out what cause this >> > page fault in mod_timer_pinned() and work around that. >> > >> > Anybody, an idea? > Wow... So I pass mod_timer_pinned() the address of a per-CPU timer while > running on that CPU, with interrupts disabled, no less. I initialize > this timer at CPU_UP_PREPARE time. So why the page fault? > > Please see below for a severe diagnostic patch.
Maybe I could help here a bit.
lappy linux # addr2line -i -e vmlinux ffffffff8111d45f /usr/src/linux/kernel/timer.c:549 /usr/src/linux/include/linux/jump_label.h:101 /usr/src/linux/include/trace/events/timer.h:44 /usr/src/linux/kernel/timer.c:601 /usr/src/linux/kernel/timer.c:734 /usr/src/linux/kernel/timer.c:886
Which means that it was about to:
debug_object_activate(timer, &timer_debug_descr);
Thanks, Sasha
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