From: Will Deacon <will.deacon@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.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 15:23:55 +0100 [thread overview]
Message-ID: <20180830142354.GB13005@arm.com> (raw)
In-Reply-To: <20180830141713.GN24082@hirez.programming.kicks-ass.net>
On Thu, Aug 30, 2018 at 04:17:13PM +0200, Peter Zijlstra wrote:
> 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).
Yeah, that's a good point. I think the !LLSC case is broken without my
patch, so we're looking at two bugs...
> 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.
Yes, that would be worth trying. However, I also just noticed that the
fetch-ops (which are now used to implement test_and_set_bit_lock()) seem
to be missing the backwards branch in the LL/SC case. Yet another diff
below.
Will
--->8
diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index 4e0072730241..f06c5ed672b3 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -84,7 +84,7 @@ static inline int atomic_fetch_##op(int i, atomic_t *v) \
"1: llock %[orig], [%[ctr]] \n" \
" " #asm_op " %[val], %[orig], %[i] \n" \
" scond %[val], [%[ctr]] \n" \
- " \n" \
+ " bnz 1b \n" \
: [val] "=&r" (val), \
[orig] "=&r" (orig) \
: [ctr] "r" (&v->counter), \
WARNING: multiple messages have this Message-ID (diff)
From: will.deacon@arm.com (Will Deacon)
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 15:23:55 +0100 [thread overview]
Message-ID: <20180830142354.GB13005@arm.com> (raw)
In-Reply-To: <20180830141713.GN24082@hirez.programming.kicks-ass.net>
On Thu, Aug 30, 2018@04:17:13PM +0200, Peter Zijlstra wrote:
> 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).
Yeah, that's a good point. I think the !LLSC case is broken without my
patch, so we're looking at two bugs...
> 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.
Yes, that would be worth trying. However, I also just noticed that the
fetch-ops (which are now used to implement test_and_set_bit_lock()) seem
to be missing the backwards branch in the LL/SC case. Yet another diff
below.
Will
--->8
diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index 4e0072730241..f06c5ed672b3 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -84,7 +84,7 @@ static inline int atomic_fetch_##op(int i, atomic_t *v) \
"1: llock %[orig], [%[ctr]] \n" \
" " #asm_op " %[val], %[orig], %[i] \n" \
" scond %[val], [%[ctr]] \n" \
- " \n" \
+ " bnz 1b \n" \
: [val] "=&r" (val), \
[orig] "=&r" (orig) \
: [ctr] "r" (&v->counter), \
WARNING: multiple messages have this Message-ID (diff)
From: will.deacon@arm.com (Will Deacon)
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 15:23:55 +0100 [thread overview]
Message-ID: <20180830142354.GB13005@arm.com> (raw)
In-Reply-To: <20180830141713.GN24082@hirez.programming.kicks-ass.net>
On Thu, Aug 30, 2018 at 04:17:13PM +0200, Peter Zijlstra wrote:
> 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).
Yeah, that's a good point. I think the !LLSC case is broken without my
patch, so we're looking at two bugs...
> 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.
Yes, that would be worth trying. However, I also just noticed that the
fetch-ops (which are now used to implement test_and_set_bit_lock()) seem
to be missing the backwards branch in the LL/SC case. Yet another diff
below.
Will
--->8
diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index 4e0072730241..f06c5ed672b3 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -84,7 +84,7 @@ static inline int atomic_fetch_##op(int i, atomic_t *v) \
"1: llock %[orig], [%[ctr]] \n" \
" " #asm_op " %[val], %[orig], %[i] \n" \
" scond %[val], [%[ctr]] \n" \
- " \n" \
+ " bnz 1b \n" \
: [val] "=&r" (val), \
[orig] "=&r" (orig) \
: [ctr] "r" (&v->counter), \
next prev parent reply other threads:[~2018-08-30 14:23 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
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 [this message]
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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