Messages in this thread | | | Subject | Re: [PATCH] mce: fix RCU lockdep from mce_log() | From | Davidlohr Bueso <> | Date | Fri, 05 Nov 2010 18:48:04 -0300 |
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Sorry, the title should have been: [PATCH] mce: fix RCU lockdep from mce_poll()
On Fri, 2010-11-05 at 18:44 -0300, Davidlohr Bueso wrote: > Hi, > > Please review this patch, I am not very familiar with MCE/RCU so I'm not sure that this is the correct fix (otherwise consider it a bug report :)). > This does "fix" the message though and I can use MCE normally. > > Thanks, > Davidlohr > > > From: Davidlohr Bueso <dave@gnu.org> > > Based on the following message: > > =================================================== > [ INFO: suspicious rcu_dereference_check() usage. ] > --------------------------------------------------- > arch/x86/kernel/cpu/mcheck/mce.c:1628 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > rcu_scheduler_active = 1, debug_locks = 1 > no locks held by mcelog/2350. > > stack backtrace: > Pid: 2350, comm: mcelog Tainted: G W 2.6.37-rc1+ #7 > Call Trace: > [<ffffffff8108e6d4>] lockdep_rcu_dereference+0xa4/0xc0 > [<ffffffff810189e9>] mce_poll+0xa9/0xd0 > [<ffffffff81160585>] do_sys_poll+0x275/0x550 > [<ffffffff8115f0e0>] ? __pollwait+0x0/0xf0 > [<ffffffff8115f1d0>] ? pollwake+0x0/0x60 > [<ffffffff8115f1d0>] ? pollwake+0x0/0x60 > [<ffffffff8130431c>] ? rcu_read_lock_held+0x2c/0x30 > [<ffffffff8130549a>] ? radix_tree_lookup_element+0xda/0x100 > [<ffffffff81121f08>] ? __do_fault+0x128/0x470 > [<ffffffff81100bdb>] ? filemap_fault+0xdb/0x4e0 > [<ffffffff810ffe75>] ? unlock_page+0x25/0x30 > [<ffffffff81069ddf>] ? sigprocmask+0x3f/0x100 > [<ffffffff8183672b>] ? _raw_spin_unlock_irq+0x2b/0x60 > [<ffffffff8108fefd>] ? trace_hardirqs_on_caller+0x13d/0x180 > [<ffffffff8108ff4d>] ? trace_hardirqs_on+0xd/0x10 > [<ffffffff8183672b>] ? _raw_spin_unlock_irq+0x2b/0x60 > [<ffffffff811608a7>] sys_ppoll+0x47/0x190 > [<ffffffff8108fefd>] ? trace_hardirqs_on_caller+0x13d/0x180 > [<ffffffff81835d39>] ? trace_hardirqs_on_thunk+0x3a/0x3f > [<ffffffff810030eb>] system_call_fastpath+0x16/0x1b > > At this point the arch/x86/kernel/cpu/mcheck/mce.c:1628 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > rcu_scheduler_active = 1, debug_locks = 1 > no locks held by mcelog/2350. > > stack backtrace: > Pid: 2350, comm: mcelog Tainted: G W 2.6.37-rc1+ #7 > Call Trace: > [<ffffffff8108e6d4>] lockdep_rcu_dereference+0xa4/0xc0 > [<ffffffff810189e9>] mce_poll+0xa9/0xd0 > [<ffffffff81160585>] do_sys_poll+0x275/0x550 > [<ffffffff8115f0e0>] ? __pollwait+0x0/0xf0 > [<ffffffff8115f1d0>] ? pollwake+0x0/0x60 > [<ffffffff8115f1d0>] ? pollwake+0x0/0x60 > [<ffffffff8130431c>] ? rcu_read_lock_held+0x2c/0x30 > [<ffffffff8130549a>] ? radix_tree_lookup_element+0xda/0x100 > [<ffffffff81121f08>] ? __do_fault+0x128/0x470 > [<ffffffff81100bdb>] ? filemap_fault+0xdb/0x4e0 > [<ffffffff810ffe75>] ? unlock_page+0x25/0x30 > [<ffffffff81069ddf>] ? sigprocmask+0x3f/0x100 > [<ffffffff8183672b>] ? _raw_spin_unlock_irq+0x2b/0x60 > [<ffffffff8108fefd>] ? trace_hardirqs_on_caller+0x13d/0x180 > [<ffffffff8108ff4d>] ? trace_hardirqs_on+0xd/0x10 > [<ffffffff8183672b>] ? _raw_spin_unlock_irq+0x2b/0x60 > [<ffffffff811608a7>] sys_ppoll+0x47/0x190 > [<ffffffff8108fefd>] ? trace_hardirqs_on_caller+0x13d/0x180 > [<ffffffff81835d39>] ? trace_hardirqs_on_thunk+0x3a/0x3f > [<ffffffff810030eb>] system_call_fastpath+0x16/0x1b > > At this point the lockdep_is_held(&mce_read_mutex) call is failing. > So check if the mce_read_mutex is held before derefencing instead of using rcu_dereference_check_mce() > > Signed-off-by: Davidlohr Bueso <dave@gnu.org> > --- > arch/x86/kernel/cpu/mcheck/mce.c | 8 ++++++-- > 1 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c > index 7a35b72..6f95b2c 100644 > --- a/arch/x86/kernel/cpu/mcheck/mce.c > +++ b/arch/x86/kernel/cpu/mcheck/mce.c > @@ -1625,8 +1625,12 @@ out: > static unsigned int mce_poll(struct file *file, poll_table *wait) > { > poll_wait(file, &mce_wait, wait); > - if (rcu_dereference_check_mce(mcelog.next)) > - return POLLIN | POLLRDNORM; > + > + if (mutex_is_locked(&mce_read_mutex)) { > + if (rcu_dereference_index_check(mcelog.next, > + rcu_read_lock_sched_held())) > + return POLLIN | POLLRDNORM; > + } > if (!mce_apei_read_done && apei_check_mce()) > return POLLIN | POLLRDNORM; > return 0; > -- > 1.7.1 > > > > -- > 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/ >
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