From: Oleg Nesterov <oleg@redhat.com>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: jeremy@goop.org, kvm@vger.kernel.org, peterz@infradead.org,
virtualization@lists.linux-foundation.org,
paul.gortmaker@windriver.com, hpa@zytor.com, ak@linux.intel.com,
a.ryabinin@samsung.com, x86@kernel.org, borntraeger@de.ibm.com,
mingo@redhat.com, xen-devel@lists.xenproject.org,
paulmck@linux.vnet.ibm.com, riel@redhat.com,
konrad.wilk@oracle.com, dave@stgolabs.net,
sasha.levin@oracle.com, davej@redhat.com, tglx@linutronix.de,
waiman.long@hp.com, linux-kernel@vger.kernel.org,
pbonzini@redhat.com, akpm@linux-foundation.org,
torvalds@linux-foundation.org
Subject: Re: [PATCH V4] x86 spinlock: Fix memory corruption on completing completions
Date: Fri, 13 Feb 2015 16:40:02 +0100 [thread overview]
Message-ID: <20150213154002.GB9535@redhat.com> (raw)
In-Reply-To: <20150213153228.GA9535@redhat.com>
On 02/13, Oleg Nesterov wrote:
>
> On 02/13, Raghavendra K T wrote:
> >
> > @@ -772,7 +773,8 @@ __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
> > * check again make sure it didn't become free while
> > * we weren't looking.
> > */
> > - if (ACCESS_ONCE(lock->tickets.head) == want) {
> > + head = READ_ONCE(lock->tickets.head);
> > + if (__tickets_equal(head, want)) {
> > add_stats(TAKEN_SLOW_PICKUP, 1);
> > goto out;
>
> This is off-topic, but with or without this change perhaps it makes sense
> to add smp_mb__after_atomic(). It is nop on x86, just to make this code
> more understandable for those (for me ;) who can never remember even the
> x86 rules.
Not that I think you should do this in v5, so please ignore.
Oleg.
WARNING: multiple messages have this Message-ID (diff)
From: Oleg Nesterov <oleg@redhat.com>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
peterz@infradead.org, torvalds@linux-foundation.org,
konrad.wilk@oracle.com, pbonzini@redhat.com,
paulmck@linux.vnet.ibm.com, waiman.long@hp.com, davej@redhat.com,
x86@kernel.org, jeremy@goop.org, paul.gortmaker@windriver.com,
ak@linux.intel.com, jasowang@redhat.com,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org,
xen-devel@lists.xenproject.org, riel@redhat.com,
borntraeger@de.ibm.com, akpm@linux-foundation.org,
a.ryabinin@samsung.com, sasha.levin@oracle.com,
dave@stgolabs.net
Subject: Re: [PATCH V4] x86 spinlock: Fix memory corruption on completing completions
Date: Fri, 13 Feb 2015 16:40:02 +0100 [thread overview]
Message-ID: <20150213154002.GB9535@redhat.com> (raw)
In-Reply-To: <20150213153228.GA9535@redhat.com>
On 02/13, Oleg Nesterov wrote:
>
> On 02/13, Raghavendra K T wrote:
> >
> > @@ -772,7 +773,8 @@ __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
> > * check again make sure it didn't become free while
> > * we weren't looking.
> > */
> > - if (ACCESS_ONCE(lock->tickets.head) == want) {
> > + head = READ_ONCE(lock->tickets.head);
> > + if (__tickets_equal(head, want)) {
> > add_stats(TAKEN_SLOW_PICKUP, 1);
> > goto out;
>
> This is off-topic, but with or without this change perhaps it makes sense
> to add smp_mb__after_atomic(). It is nop on x86, just to make this code
> more understandable for those (for me ;) who can never remember even the
> x86 rules.
Not that I think you should do this in v5, so please ignore.
Oleg.
next prev parent reply other threads:[~2015-02-13 15:40 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-13 6:45 [PATCH V4] x86 spinlock: Fix memory corruption on completing completions Raghavendra K T
2015-02-13 6:45 ` Raghavendra K T
2015-02-13 6:45 ` Raghavendra K T
2015-02-13 15:32 ` Oleg Nesterov
2015-02-13 15:32 ` Oleg Nesterov
2015-02-13 15:32 ` Oleg Nesterov
2015-02-13 15:40 ` Oleg Nesterov [this message]
2015-02-13 15:40 ` Oleg Nesterov
2015-02-13 15:40 ` Oleg Nesterov
2015-02-15 5:47 ` Raghavendra K T
2015-02-15 5:47 ` Raghavendra K T
2015-02-15 16:07 ` Oleg Nesterov
2015-02-15 16:07 ` Oleg Nesterov
2015-02-15 16:07 ` Oleg Nesterov
2015-02-15 5:47 ` Raghavendra K T
-- strict thread matches above, loose matches on Subject: below --
2015-02-13 6:45 Raghavendra K T
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