From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
To: Tahsin Erdogan <tahsin@google.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
x86@kernel.org, peterz@infradead.org, Waiman.Long@hp.com,
borntraeger@de.ibm.com, oleg@redhat.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/spinlocks: Fix regression in spinlock contention detection
Date: Wed, 06 May 2015 21:07:01 +0530 [thread overview]
Message-ID: <554A351D.8060700@linux.vnet.ibm.com> (raw)
In-Reply-To: <1430799331-20445-1-git-send-email-tahsin@google.com>
On 05/05/2015 09:45 AM, Tahsin Erdogan wrote:
> A spinlock is regarded as contended when there is at least one waiter.
> Currently, the code that checks whether there are any waiters rely on
> tail value being greater than head. However, this is not true if tail
> reaches the max value and wraps back to zero, so arch_spin_is_contended()
> incorrectly returns 0 (not contended) when tail is smaller than head.
>
> The original code (before regression) handled this case by casting the
> (tail - head) to an unsigned value. This change simply restores that
> behavior.
>
> Fixes: d6abfdb20223 ("x86/spinlocks/paravirt: Fix memory corruption on
> unlock")
> Signed-off-by: Tahsin Erdogan <tahsin@google.com>
> ---
Tahsin,
Perhaps we need to CC stable (3.19) too..?
next prev parent reply other threads:[~2015-05-06 15:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-05 4:15 [PATCH] x86/spinlocks: Fix regression in spinlock contention detection Tahsin Erdogan
2015-05-05 9:06 ` [tip:x86/urgent] " tip-bot for Tahsin Erdogan
2015-05-05 9:17 ` [PATCH] " Peter Zijlstra
2015-05-05 10:38 ` Raghavendra K T
2015-05-05 10:58 ` Peter Zijlstra
2015-05-05 14:10 ` Tahsin Erdogan
2015-05-05 14:30 ` Peter Zijlstra
[not found] ` <CAAeU0aPSDdDVKm=YgbYH+SWfk07rLGgEFMQoN+nt4vc1_YLHzg@mail.gmail.com>
2015-05-05 15:25 ` Raghavendra K T
2015-05-05 15:28 ` Tahsin Erdogan
2015-05-05 15:32 ` Waiman Long
2015-05-05 15:38 ` Raghavendra K T
2015-05-06 15:37 ` Raghavendra K T [this message]
2015-05-07 7:13 ` Tahsin Erdogan
2015-05-08 11:09 ` Greg KH
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