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Subject[tip:ras/urgent] x86/mce: Make the MCE notifier a blocking one
Commit-ID:  0dc9c639e6553e39c13b2c0d54c8a1b098cb95e2
Gitweb: http://git.kernel.org/tip/0dc9c639e6553e39c13b2c0d54c8a1b098cb95e2
Author: Vishal Verma <vishal.l.verma@intel.com>
AuthorDate: Tue, 18 Apr 2017 20:42:35 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 18 Apr 2017 22:23:48 +0200

x86/mce: Make the MCE notifier a blocking one

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
___might_sleep
__might_sleep
mutex_lock_nested
? __lock_acquire
nfit_handle_mce
notifier_call_chain
atomic_notifier_call_chain
? atomic_notifier_call_chain
mce_gen_pool_process

Convert the notifier to a blocking one which gets to run only in process
context.

Boris: remove the notifier call in atomic context in print_mce(). For
now, let's print the MCE on the atomic path so that we can make sure
they go out and get logged at least.

Fixes: 6839a6d96f4e ("nfit: do an ARS scrub on hitting a latent media error")
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Acked-by: Tony Luck <tony.luck@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20170411224457.24777-1-vishal.l.verma@intel.com
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
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 | 17 +++--------------
3 files changed, 5 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce-genpool.c b/arch/x86/kernel/cpu/mcheck/mce-genpool.c
index 1e5a50c..217cd44 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-genpool.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-genpool.c
@@ -85,7 +85,7 @@ void mce_gen_pool_process(struct work_struct *__unused)
head = llist_reverse_order(head);
llist_for_each_entry_safe(node, tmp, head, llnode) {
mce = &node->mce;
- atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
+ blocking_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));
}
}
diff --git a/arch/x86/kernel/cpu/mcheck/mce-internal.h b/arch/x86/kernel/cpu/mcheck/mce-internal.h
index 903043e..19592ba 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-internal.h
+++ b/arch/x86/kernel/cpu/mcheck/mce-internal.h
@@ -13,7 +13,7 @@ enum severity_level {
MCE_PANIC_SEVERITY,
};

-extern struct atomic_notifier_head x86_mce_decoder_chain;
+extern struct blocking_notifier_head x86_mce_decoder_chain;

#define ATTR_LEN 16
#define INITIAL_CHECK_INTERVAL 5 * 60 /* 5 minutes */
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 5accfbd..af44ebe 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -123,7 +123,7 @@ static void (*quirk_no_way_out)(int bank, struct mce *m, struct pt_regs *regs);
* CPU/chipset specific EDAC code can register a notifier call here to print
* MCE errors in a human-readable form.
*/
-ATOMIC_NOTIFIER_HEAD(x86_mce_decoder_chain);
+BLOCKING_NOTIFIER_HEAD(x86_mce_decoder_chain);

/* Do initial initialization of a struct mce */
void mce_setup(struct mce *m)
@@ -220,7 +220,7 @@ void mce_register_decode_chain(struct notifier_block *nb)

WARN_ON(nb->priority > MCE_PRIO_LOWEST && nb->priority < MCE_PRIO_EDAC);

- atomic_notifier_chain_register(&x86_mce_decoder_chain, nb);
+ blocking_notifier_chain_register(&x86_mce_decoder_chain, nb);
}
EXPORT_SYMBOL_GPL(mce_register_decode_chain);

@@ -228,7 +228,7 @@ void mce_unregister_decode_chain(struct notifier_block *nb)
{
atomic_dec(&num_notifiers);

- atomic_notifier_chain_unregister(&x86_mce_decoder_chain, nb);
+ blocking_notifier_chain_unregister(&x86_mce_decoder_chain, nb);
}
EXPORT_SYMBOL_GPL(mce_unregister_decode_chain);

@@ -321,18 +321,7 @@ static void __print_mce(struct mce *m)

static void print_mce(struct mce *m)
{
- int ret = 0;
-
__print_mce(m);
-
- /*
- * Print out human-readable details about the MCE error,
- * (if the CPU has an implementation for that)
- */
- ret = atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, m);
- if (ret == NOTIFY_STOP)
- return;
-
pr_emerg_ratelimited(HW_ERR "Run the above through 'mcelog --ascii'\n");
}

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