linux-kernel - [PATCH 05/13] x86/mce: Avoid potential deadlock due to printk() in MCE context

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Date:	Wed, 12 Aug 2015 18:29:37 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Tony Luck <tony.luck@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 05/13] x86/mce: Avoid potential deadlock due to printk() in MCE context

From: "Chen, Gong" <gong.chen@...ux.intel.com>

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>
Link: http://lkml.kernel.org/r/1432150538-3120-5-git-send-email-gong.chen@linux.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>
---
 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 a1aef9533154..34c89a3e8260 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 82603690b65c..9568bb55bfe2 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 844f56c5616d..70f567f774ed 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();
 }
 
 /*
-- 
2.5.0.rc2.28.g6003e7f

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