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From: Peter Zijlstra <peterz@infradead.org>
To: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Cc: "will.deacon@arm.com" <will.deacon@arm.com>,
	"mingo@kernel.org" <mingo@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Alexey.Brodkin@synopsys.com" <Alexey.Brodkin@synopsys.com>,
	"Vineet.Gupta1@synopsys.com" <Vineet.Gupta1@synopsys.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"linux-snps-arc@lists.infradead.org" 
	<linux-snps-arc@lists.infradead.org>,
	"yamada.masahiro@socionext.com" <yamada.masahiro@socionext.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: Re: Patch "asm-generic/bitops/lock.h: Rewrite using atomic_fetch_" causes kernel crash
Date: Thu, 30 Aug 2018 16:17:13 +0200	[thread overview]
Message-ID: <20180830141713.GN24082@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1535629996.4465.44.camel@synopsys.com>

On Thu, Aug 30, 2018 at 11:53:17AM +0000, Eugeniy Paltsev wrote:
> I can see crashes with LLSC enabled in both SMP running on 4 cores
> and SMP running on 1 core.

So you're running on LL/SC enabled hardware; that would make Will's
patch irrelevant (although still a good idea for the hardware that does
care about that spinlocked atomic crud).

Does something like the below cure things? That would confirm the
suggestion that the change to __clear_bit_unlock() is the curprit.

If that doesn't cure things, then we've been looking in entirely the
wrong place.

---
diff --git a/include/asm-generic/bitops/lock.h b/include/asm-generic/bitops/lock.h
index 3ae021368f48..79c6978152f8 100644
--- a/include/asm-generic/bitops/lock.h
+++ b/include/asm-generic/bitops/lock.h
@@ -57,12 +57,7 @@ static inline void clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
 static inline void __clear_bit_unlock(unsigned int nr,
 				      volatile unsigned long *p)
 {
-	unsigned long old;
-
-	p += BIT_WORD(nr);
-	old = READ_ONCE(*p);
-	old &= ~BIT_MASK(nr);
-	atomic_long_set_release((atomic_long_t *)p, old);
+	clear_bit_unlock(nr, p);
 }
 
 /**

WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"Vineet.Gupta1@synopsys.com" <Vineet.Gupta1@synopsys.com>,
	"Alexey.Brodkin@synopsys.com" <Alexey.Brodkin@synopsys.com>,
	"will.deacon@arm.com" <will.deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"yamada.masahiro@socionext.com" <yamada.masahiro@socionext.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"linux-snps-arc@lists.infradead.org"
	<linux-snps-arc@lists.infradead.org>,
	"mingo@kernel.org" <mingo@kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: Patch "asm-generic/bitops/lock.h: Rewrite using atomic_fetch_" causes kernel crash
Date: Thu, 30 Aug 2018 16:17:13 +0200	[thread overview]
Message-ID: <20180830141713.GN24082@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1535629996.4465.44.camel@synopsys.com>

On Thu, Aug 30, 2018 at 11:53:17AM +0000, Eugeniy Paltsev wrote:
> I can see crashes with LLSC enabled in both SMP running on 4 cores
> and SMP running on 1 core.

So you're running on LL/SC enabled hardware; that would make Will's
patch irrelevant (although still a good idea for the hardware that does
care about that spinlocked atomic crud).

Does something like the below cure things? That would confirm the
suggestion that the change to __clear_bit_unlock() is the curprit.

If that doesn't cure things, then we've been looking in entirely the
wrong place.

---
diff --git a/include/asm-generic/bitops/lock.h b/include/asm-generic/bitops/lock.h
index 3ae021368f48..79c6978152f8 100644
--- a/include/asm-generic/bitops/lock.h
+++ b/include/asm-generic/bitops/lock.h
@@ -57,12 +57,7 @@ static inline void clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
 static inline void __clear_bit_unlock(unsigned int nr,
 				      volatile unsigned long *p)
 {
-	unsigned long old;
-
-	p += BIT_WORD(nr);
-	old = READ_ONCE(*p);
-	old &= ~BIT_MASK(nr);
-	atomic_long_set_release((atomic_long_t *)p, old);
+	clear_bit_unlock(nr, p);
 }
 
 /**

WARNING: multiple messages have this Message-ID (diff)
From: peterz@infradead.org (Peter Zijlstra)
To: linux-snps-arc@lists.infradead.org
Subject: Patch "asm-generic/bitops/lock.h: Rewrite using atomic_fetch_" causes kernel crash
Date: Thu, 30 Aug 2018 16:17:13 +0200	[thread overview]
Message-ID: <20180830141713.GN24082@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1535629996.4465.44.camel@synopsys.com>

On Thu, Aug 30, 2018@11:53:17AM +0000, Eugeniy Paltsev wrote:
> I can see crashes with LLSC enabled in both SMP running on 4 cores
> and SMP running on 1 core.

So you're running on LL/SC enabled hardware; that would make Will's
patch irrelevant (although still a good idea for the hardware that does
care about that spinlocked atomic crud).

Does something like the below cure things? That would confirm the
suggestion that the change to __clear_bit_unlock() is the curprit.

If that doesn't cure things, then we've been looking in entirely the
wrong place.

---
diff --git a/include/asm-generic/bitops/lock.h b/include/asm-generic/bitops/lock.h
index 3ae021368f48..79c6978152f8 100644
--- a/include/asm-generic/bitops/lock.h
+++ b/include/asm-generic/bitops/lock.h
@@ -57,12 +57,7 @@ static inline void clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
 static inline void __clear_bit_unlock(unsigned int nr,
 				      volatile unsigned long *p)
 {
-	unsigned long old;
-
-	p += BIT_WORD(nr);
-	old = READ_ONCE(*p);
-	old &= ~BIT_MASK(nr);
-	atomic_long_set_release((atomic_long_t *)p, old);
+	clear_bit_unlock(nr, p);
 }
 
 /**

WARNING: multiple messages have this Message-ID (diff)
From: peterz@infradead.org (Peter Zijlstra)
To: linux-arm-kernel@lists.infradead.org
Subject: Patch "asm-generic/bitops/lock.h: Rewrite using atomic_fetch_" causes kernel crash
Date: Thu, 30 Aug 2018 16:17:13 +0200	[thread overview]
Message-ID: <20180830141713.GN24082@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1535629996.4465.44.camel@synopsys.com>

On Thu, Aug 30, 2018 at 11:53:17AM +0000, Eugeniy Paltsev wrote:
> I can see crashes with LLSC enabled in both SMP running on 4 cores
> and SMP running on 1 core.

So you're running on LL/SC enabled hardware; that would make Will's
patch irrelevant (although still a good idea for the hardware that does
care about that spinlocked atomic crud).

Does something like the below cure things? That would confirm the
suggestion that the change to __clear_bit_unlock() is the curprit.

If that doesn't cure things, then we've been looking in entirely the
wrong place.

---
diff --git a/include/asm-generic/bitops/lock.h b/include/asm-generic/bitops/lock.h
index 3ae021368f48..79c6978152f8 100644
--- a/include/asm-generic/bitops/lock.h
+++ b/include/asm-generic/bitops/lock.h
@@ -57,12 +57,7 @@ static inline void clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
 static inline void __clear_bit_unlock(unsigned int nr,
 				      volatile unsigned long *p)
 {
-	unsigned long old;
-
-	p += BIT_WORD(nr);
-	old = READ_ONCE(*p);
-	old &= ~BIT_MASK(nr);
-	atomic_long_set_release((atomic_long_t *)p, old);
+	clear_bit_unlock(nr, p);
 }
 
 /**

  parent reply	other threads:[~2018-08-30 14:17 UTC|newest]

Thread overview: 89+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-29 18:33 Patch "asm-generic/bitops/lock.h: Rewrite using atomic_fetch_" causes kernel crash Eugeniy Paltsev
2018-08-29 18:33 ` Eugeniy Paltsev
2018-08-29 18:33 ` Eugeniy Paltsev
2018-08-29 18:33 ` Eugeniy Paltsev
2018-08-29 21:16 ` Vineet Gupta
2018-08-29 21:16   ` Vineet Gupta
2018-08-29 21:16   ` Vineet Gupta
2018-08-29 21:16   ` Vineet Gupta
2018-08-30  9:35   ` Will Deacon
2018-08-30  9:35     ` Will Deacon
2018-08-30  9:35     ` Will Deacon
2018-08-30  9:35     ` Will Deacon
2018-08-30  9:44   ` Peter Zijlstra
2018-08-30  9:44     ` Peter Zijlstra
2018-08-30  9:44     ` Peter Zijlstra
2018-08-30  9:44     ` Peter Zijlstra
2018-08-30  9:44     ` Peter Zijlstra
2018-08-30  9:51     ` Will Deacon
2018-08-30  9:51       ` Will Deacon
2018-08-30  9:51       ` Will Deacon
2018-08-30  9:51       ` Will Deacon
2018-08-30 11:53       ` Eugeniy Paltsev
2018-08-30 11:53         ` Eugeniy Paltsev
2018-08-30 11:53         ` Eugeniy Paltsev
2018-08-30 11:53         ` Eugeniy Paltsev
2018-08-30 13:57         ` Will Deacon
2018-08-30 13:57           ` Will Deacon
2018-08-30 13:57           ` Will Deacon
2018-08-30 13:57           ` Will Deacon
2018-08-30 14:17         ` Peter Zijlstra [this message]
2018-08-30 14:17           ` Peter Zijlstra
2018-08-30 14:17           ` Peter Zijlstra
2018-08-30 14:17           ` Peter Zijlstra
2018-08-30 14:17           ` Peter Zijlstra
2018-08-30 14:23           ` Will Deacon
2018-08-30 14:23             ` Will Deacon
2018-08-30 14:23             ` Will Deacon
2018-08-30 14:23             ` Will Deacon
2018-08-30 14:29             ` Peter Zijlstra
2018-08-30 14:29               ` Peter Zijlstra
2018-08-30 14:29               ` Peter Zijlstra
2018-08-30 14:29               ` Peter Zijlstra
2018-08-30 14:43               ` Peter Zijlstra
2018-08-30 14:43                 ` Peter Zijlstra
2018-08-30 14:43                 ` Peter Zijlstra
2018-08-30 14:43                 ` Peter Zijlstra
2018-08-30 14:43                 ` Peter Zijlstra
2020-04-14  1:19                 ` Vineet Gupta
2020-04-14  1:19                   ` Vineet Gupta
2020-04-14  1:19                   ` Vineet Gupta
2020-04-14  1:19                   ` Vineet Gupta
2018-08-30 20:31               ` Vineet Gupta
2018-08-30 20:31                 ` Vineet Gupta
2018-08-30 20:31                 ` Vineet Gupta
2018-08-30 20:31                 ` Vineet Gupta
2018-08-30 20:45                 ` Peter Zijlstra
2018-08-30 20:45                   ` Peter Zijlstra
2018-08-30 20:45                   ` Peter Zijlstra
2018-08-30 20:45                   ` Peter Zijlstra
2018-08-30 20:45                   ` Peter Zijlstra
2018-08-31  0:30                   ` Vineet Gupta
2018-08-31  0:30                     ` Vineet Gupta
2018-08-31  0:30                     ` Vineet Gupta
2018-08-31  0:30                     ` Vineet Gupta
2018-08-31  9:53                     ` Will Deacon
2018-08-31  9:53                       ` Will Deacon
2018-08-31  9:53                       ` Will Deacon
2018-08-31  9:53                       ` Will Deacon
2018-08-30 14:46           ` Eugeniy Paltsev
2018-08-30 14:46             ` Eugeniy Paltsev
2018-08-30 14:46             ` Eugeniy Paltsev
2018-08-30 14:46             ` Eugeniy Paltsev
2018-08-30 14:46             ` Eugeniy Paltsev
2018-08-30 17:15             ` Peter Zijlstra
2018-08-30 17:15               ` Peter Zijlstra
2018-08-30 17:15               ` Peter Zijlstra
2018-08-30 17:15               ` Peter Zijlstra
2018-08-31  0:42       ` Vineet Gupta
2018-08-31  0:42         ` Vineet Gupta
2018-08-31  0:42         ` Vineet Gupta
2018-08-31  0:42         ` Vineet Gupta
2018-08-31  0:29     ` __clear_bit_lock to use atomic clear_bit (was Re: Patch "asm-generic/bitops/lock.h) Vineet Gupta
2018-08-31  0:29       ` Vineet Gupta
2018-08-31  0:29       ` Vineet Gupta
2018-08-31  0:29       ` Vineet Gupta
2018-08-31  7:24       ` Peter Zijlstra
2018-08-31  7:24         ` Peter Zijlstra
2018-08-31  7:24         ` Peter Zijlstra
2018-08-31  7:24         ` Peter Zijlstra

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