linux-kernel - [tip:ras/core] x86/mce: Avoid potential deadlock due to printk() in MCE context

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Message-ID: <tip-f29a7aff4bd60ebc3da4982f80144a4158c4c74a@git.kernel.org>
Date:	Thu, 13 Aug 2015 03:47:24 -0700
From:	"tip-bot for Chen, Gong" <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	gong.chen@...ux.intel.com, bp@...e.de, tglx@...utronix.de,
	xiexiuqi@...wei.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	tony.luck@...el.com, torvalds@...ux-foundation.org,
	peterz@...radead.org, mingo@...nel.org
Subject: [tip:ras/core] x86/mce: Avoid potential deadlock due to printk()
  in MCE context

Commit-ID:  f29a7aff4bd60ebc3da4982f80144a4158c4c74a
Gitweb:     http://git.kernel.org/tip/f29a7aff4bd60ebc3da4982f80144a4158c4c74a
Author:     Chen, Gong <gong.chen@...ux.intel.com>
AuthorDate: Wed, 12 Aug 2015 18:29:37 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 13 Aug 2015 10:12:51 +0200

x86/mce: Avoid potential deadlock due to printk() in MCE context

Printing in MCE context is a no-no, currently, as printk() is
not NMI-safe. If some of the notifiers on the MCE chain call do
so, we may deadlock. In order to avoid that, delay printk() to
process context where it is safe.

Reported-by: Xie XiuQi <xiexiuqi@...wei.com>
Signed-off-by: Chen, Gong <gong.chen@...ux.intel.com>
[ Fold in subsequent patch from Boris for early boot logging. ]
Signed-off-by: Tony Luck <tony.luck@...el.com>
[ Kick irq_work in mce_log() directly. ]
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1439396985-12812-6-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/cpu/mcheck/mce-apei.c  | 1 -
 arch/x86/kernel/cpu/mcheck/mce.c       | 4 ++--
 arch/x86/kernel/cpu/mcheck/mce_intel.c | 1 -
 3 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce-apei.c b/arch/x86/kernel/cpu/mcheck/mce-apei.c
index a1aef95..34c89a3 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-apei.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-apei.c
@@ -57,7 +57,6 @@ void apei_mce_report_mem_error(int severity, struct cper_sec_mem_err *mem_err)
 
 	m.addr = mem_err->physical_addr;
 	mce_log(&m);
-	mce_notify_irq();
 }
 EXPORT_SYMBOL_GPL(apei_mce_report_mem_error);
 
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 8260369..9568bb5 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -159,7 +159,8 @@ void mce_log(struct mce *mce)
 	/* Emit the trace record: */
 	trace_mce_record(mce);
 
-	atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
+	if (!mce_gen_pool_add(mce))
+		irq_work_queue(&mce_irq_work);
 
 	mce->finished = 0;
 	wmb();
@@ -1122,7 +1123,6 @@ void do_machine_check(struct pt_regs *regs, long error_code)
 		/* assuming valid severity level != 0 */
 		m.severity = severity;
 		m.usable_addr = mce_usable_address(&m);
-		mce_gen_pool_add(&m);
 
 		mce_log(&m);
 
diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c
index 844f56c..70f567f 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -246,7 +246,6 @@ static void intel_threshold_interrupt(void)
 		return;
 
 	machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned));
-	mce_notify_irq();
 }
 
 /*
--
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