Re: [PATCH 4/4 Rebase] x86, MCE: Avoid potential deadlock in MCE context

["Chen, Gong" <gong.chen@linux.intel.com>]

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On Wed, May 20, 2015 at 11:28:00AM +0200, Borislav Petkov wrote:
> Date: Wed, 20 May 2015 11:28:00 +0200
> From: Borislav Petkov <bp@suse.de>
> To: "Chen, Gong" <gong.chen@linux.intel.com>, tony.luck@intel.com
> Cc: linux-kernel@vger.kernel.org
> Subject: Re: [PATCH 4/4 Rebase] x86, MCE: Avoid potential deadlock in MCE
>  context
> User-Agent: Mutt/1.5.23 (2014-03-12)
> 
> On Wed, May 20, 2015 at 03:35:38PM -0400, Chen, Gong wrote:
> > 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 *printk*, we
> > may deadlock. In order to avoid that, delay printk into process context
> > to fix it.
> > 
> > Background info at: https://lkml.org/lkml/2014/6/27/26
> > 
> > Reported-by: Xie XiuQi <xiexiuqi@huawei.com>
> > Signed-off-by: Chen, Gong <gong.chen@linux.intel.com>
> > Link: http://lkml.kernel.org/r/1406797523-28710-6-git-send-email-gong.chen@linux.intel.com
> > [ Boris: rewrite a bit. ]
> > Signed-off-by: Borislav Petkov <bp@suse.de>
> > ---
> >  arch/x86/include/asm/mce.h               | 1 +
> >  arch/x86/kernel/cpu/mcheck/mce-apei.c    | 2 +-
> >  arch/x86/kernel/cpu/mcheck/mce.c         | 8 ++++++--
> >  arch/x86/kernel/cpu/mcheck/mce_intel.c   | 1 -
> >  arch/x86/kernel/cpu/mcheck/therm_throt.c | 1 +
> >  arch/x86/kernel/cpu/mcheck/threshold.c   | 1 +
> >  6 files changed, 10 insertions(+), 4 deletions(-)
> 
> ....
> 
> > diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c b/arch/x86/kernel/cpu/mcheck/therm_throt.c
> > index 1af51b1586d7..2733f275237d 100644
> > --- a/arch/x86/kernel/cpu/mcheck/therm_throt.c
> > +++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c
> > @@ -427,6 +427,7 @@ static inline void __smp_thermal_interrupt(void)
> >  {
> >  	inc_irq_stat(irq_thermal_count);
> >  	smp_thermal_vector();
> > +	mce_queue_irq_work();
> 
> Hmm, at a second glance, this looks wrong. I think we should do that
> call in intel_thermal_interrupt().
> 
> >  asmlinkage __visible void smp_thermal_interrupt(struct pt_regs *regs)
> > diff --git a/arch/x86/kernel/cpu/mcheck/threshold.c b/arch/x86/kernel/cpu/mcheck/threshold.c
> > index 7245980186ee..d695faa234eb 100644
> > --- a/arch/x86/kernel/cpu/mcheck/threshold.c
> > +++ b/arch/x86/kernel/cpu/mcheck/threshold.c
> > @@ -22,6 +22,7 @@ static inline void __smp_threshold_interrupt(void)
> >  {
> >  	inc_irq_stat(irq_threshold_count);
> >  	mce_threshold_vector();
> > +	mce_queue_irq_work();
> 
> Same here.
> 
> mce_queue_irq_work() call should be issued in both AMD and Intel
> threshold handlers but not in the generic one which is unlikely to queue
> any MCE...
> 
> Right?
> 
Since AMD doesn't queue any MCE, it should definitely only cover Intel.
Please check out following patch:

----8<----
From: "Chen, Gong" <gong.chen@linux.intel.com>
Date: Fri, 22 May 2015 17:02:50 -0400
Subject: [PATCH 4/4 rebase v2] x86, MCE: Avoid potential deadlock 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 *printk*, we
may deadlock. In order to avoid that, delay printk into process context
to fix it.

Background info at: https://lkml.org/lkml/2014/6/27/26

v2 -> v1: move mce_queue_irq_work call into Intel specific logic

Reported-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Chen, Gong <gong.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/1406797523-28710-6-git-send-email-gong.chen@linux.intel.com
[ Boris: rewrite a bit. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/include/asm/mce.h               | 1 +
 arch/x86/kernel/cpu/mcheck/mce-apei.c    | 2 +-
 arch/x86/kernel/cpu/mcheck/mce.c         | 8 ++++++--
 arch/x86/kernel/cpu/mcheck/mce_intel.c   | 2 +-
 arch/x86/kernel/cpu/mcheck/therm_throt.c | 2 ++
 5 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index d16f983f46f5..781432dd8123 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -198,6 +198,7 @@ enum mcp_flags {
 bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
 
 int mce_notify_irq(void);
+void mce_queue_irq_work(void);
 
 DECLARE_PER_CPU(struct mce, injectm);
 
diff --git a/arch/x86/kernel/cpu/mcheck/mce-apei.c b/arch/x86/kernel/cpu/mcheck/mce-apei.c
index a1aef9533154..380e3ac8fb62 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-apei.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-apei.c
@@ -57,7 +57,7 @@ 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();
+	mce_queue_irq_work();
 }
 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 b369b5fcda1d..a3be97961e22 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -156,7 +156,7 @@ void mce_log(struct mce *mce)
 	/* Emit the trace record: */
 	trace_mce_record(mce);
 
-	atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
+	mce_genpool_add(mce);
 
 	mce->finished = 0;
 	wmb();
@@ -486,6 +486,11 @@ static void mce_irq_work_cb(struct irq_work *entry)
 	mce_schedule_work();
 }
 
+void mce_queue_irq_work(void)
+{
+	irq_work_queue(&mce_irq_work);
+}
+
 static void mce_report_event(struct pt_regs *regs)
 {
 	if (regs->flags & (X86_VM_MASK|X86_EFLAGS_IF)) {
@@ -1105,7 +1110,6 @@ 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_genpool_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 b4a41cf030ed..3392002e2911 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -216,7 +216,7 @@ static void intel_threshold_interrupt(void)
 		return;
 
 	machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned));
-	mce_notify_irq();
+	mce_queue_irq_work();
 }
 
 /*
diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c b/arch/x86/kernel/cpu/mcheck/therm_throt.c
index 1af51b1586d7..809a1e8f7fbd 100644
--- a/arch/x86/kernel/cpu/mcheck/therm_throt.c
+++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c
@@ -413,6 +413,8 @@ static void intel_thermal_interrupt(void)
 					POWER_LIMIT_EVENT,
 					PACKAGE_LEVEL);
 	}
+
+	mce_queue_irq_work();
 }
 
 static void unexpected_thermal_interrupt(void)
-- 
2.3.2


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