Messages in this thread | | | Date | Wed, 12 Apr 2017 11:14:42 +0200 | From | Borislav Petkov <> | Subject | Re: [RFC PATCH] x86, mce: change the mce notifier to 'blocking' from 'atomic' |
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On Tue, Apr 11, 2017 at 04:44:57PM -0600, Vishal Verma wrote: > The NFIT MCE handler callback (for handling media errors on NVDIMMs) > takes a mutex to add the location of a memory error to a list. But since > the notifier call chain for machine checks (x86_mce_decoder_chain) is > atomic, we get a lockdep splat like: > > BUG: sleeping function called from invalid context at kernel/locking/mutex.c:620 > in_atomic(): 1, irqs_disabled(): 0, pid: 4, name: kworker/0:0 > [..] > Call Trace: > dump_stack+0x86/0xc3 > ___might_sleep+0x178/0x240 > __might_sleep+0x4a/0x80 > mutex_lock_nested+0x43/0x3f0 > ? __lock_acquire+0xcbc/0x1290 > nfit_handle_mce+0x33/0x180 [nfit] > notifier_call_chain+0x4a/0x70 > atomic_notifier_call_chain+0x6e/0x110 > ? atomic_notifier_call_chain+0x5/0x110 > mce_gen_pool_process+0x41/0x70 > > Commit 648ed94038c030245a06e4be59744fd5cdc18c40 > x86/mce: Provide a lockless memory pool to save error records > Changes the mce notifier callbacks to be run in a process context, and > this can allow us to use the 'blocking' type notifier, where we can take > mutexes etc. in the call chain functions. > > Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com> > Cc: Borislav Petkov <bp@suse.de> > Cc: Tony Luck <tony.luck@intel.com> > Cc: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> > --- > arch/x86/kernel/cpu/mcheck/mce-genpool.c | 2 +- > arch/x86/kernel/cpu/mcheck/mce-internal.h | 2 +- > arch/x86/kernel/cpu/mcheck/mce.c | 8 ++++---- > 3 files changed, 6 insertions(+), 6 deletions(-) > > While this patch almost solves the problem, I think it is not quite right. > The x86_mce_decoder_chain is also called from print_mce for fatal machine > checks, and that is, afaict, still from an atomic context. One thing Tony > suggested was splitting the notifier chain into two distinct chains, one > for regular logging and recoverable actions that allows blocking, the > other from the panic path.
Well, if Mohammad won't come to the mountain...
So the NFIT handler has:
/* We only care about memory errors */ if (!(mce->status & MCACOD)) return NOTIFY_DONE;
what severity are we talking here? Errors which can be reported on the panic path, i.e., in atomic context or only AO/AR ones which don't raise an #MC exception?
-- Regards/Gruss, Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
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