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RE: [PATCH V2] arm64: traps: disable irq in die()

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  RE: [PATCH V2] arm64: traps: disable irq in die() Zhou Qiao(周侨) <qiaozhou@asrmicro.com> - 2017-07-21 09:40 +0200
    Re: [PATCH V2] arm64: traps: disable irq in die() Will Deacon <will.deacon@arm.com> - 2017-07-21 10:40 +0200
      Re: [PATCH V2] arm64: traps: disable irq in die() qiaozhou <qiaozhou@asrmicro.com> - 2017-07-21 12:00 +0200

#1693449 — RE: [PATCH V2] arm64: traps: disable irq in die()

Hi Maintainers,

Could you please help to take a look and give some comments? Thanks in advance.

Best Regards
Qiao

-----Original Message-----
From: Zhou Qiao
Sent: Friday, July 07, 2017 5:30 PM
To: catalin.marinas@arm.com; will.deacon@arm.com; mark.rutland@arm.com; suzuki.poulose@arm.com; mingo@kernel.org; marc.zyngier@arm.com; andre.przywara@arm.com; linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org
Cc: Zhou Qiao
Subject: [PATCH V2] arm64: traps: disable irq in die()

In current die(), the irq is disabled for __die() handle, not including the possible panic() handling. Since the log in __die() can take several hundreds ms, new irq might come and interrupt current die().

If the process calling die() holds some critical resource, and some other process scheduled later also needs it, then it would deadlock.
The first panic will not be executed.

So here disable irq for the whole flow of die().

Signed-off-by: Qiao Zhou <qiaozhou@asrmicro.com>
---
 arch/arm64/kernel/traps.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 0805b44..2e2ff88 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -274,10 +274,12 @@ static DEFINE_RAW_SPINLOCK(die_lock);  void die(const char *str, struct pt_regs *regs, int err)  {
 	int ret;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&die_lock, flags);
 
 	oops_enter();
 
-	raw_spin_lock_irq(&die_lock);
 	console_verbose();
 	bust_spinlocks(1);
 	ret = __die(str, err, regs);
@@ -287,13 +289,15 @@ void die(const char *str, struct pt_regs *regs, int err)
 
 	bust_spinlocks(0);
 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
-	raw_spin_unlock_irq(&die_lock);
 	oops_exit();
 
 	if (in_interrupt())
 		panic("Fatal exception in interrupt");
 	if (panic_on_oops)
 		panic("Fatal exception");
+
+	raw_spin_unlock_irqrestore(&die_lock, flags);
+
 	if (ret != NOTIFY_STOP)
 		do_exit(SIGSEGV);
 }
--
2.7.4

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#1693474

On Fri, Jul 21, 2017 at 07:38:42AM +0000, Zhou Qiao(周侨) wrote:
> Could you please help to take a look and give some comments? Thanks in
> advance.

I've queued this on the arm64 for-next/fixes/core branch.

Will

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#1693549

On 2017年07月21日 16:32, Will Deacon wrote:
> On Fri, Jul 21, 2017 at 07:38:42AM +0000, Zhou Qiao(周侨) wrote:
>> Could you please help to take a look and give some comments? Thanks in
>> advance.
> I've queued this on the arm64 for-next/fixes/core branch.
Got it. Thanks!
>
> Will
Best Regards
Qiao

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