From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
linux-arch@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org,
Alexander Graf <agraf@suse.de>, Paul Mackerras <paulus@samba.org>,
David Vrabel <david.vrabel@citrix.com>,
xen-devel@lists.xenproject.org,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2 3/3] sched/preempt: fix cond_resched_lock() and cond_resched_softirq()
Date: Wed, 15 Jul 2015 15:52:34 +0300 [thread overview]
Message-ID: <55A65792.80903@yandex-team.ru> (raw)
In-Reply-To: <1436962596.1026.10.camel@edumazet-glaptop2.roam.corp.google.com>
On 15.07.2015 15:16, Eric Dumazet wrote:
> On Wed, 2015-07-15 at 12:52 +0300, Konstantin Khlebnikov wrote:
>> These functions check should_resched() before unlocking spinlock/bh-enable:
>> preempt_count always non-zero => should_resched() always returns false.
>> cond_resched_lock() worked iff spin_needbreak is set.
>
> Interesting, this definitely used to work (linux-3.11)
>
> Any idea of which commit broke things ?
>
Searching... done
This one: bdb43806589096ac4272fe1307e789846ac08d7c in v3.13
before
-static inline int should_resched(void)
-{
- return need_resched() && !(preempt_count() & PREEMPT_ACTIVE);
-}
after
+static __always_inline bool should_resched(void)
+{
+ return unlikely(!*preempt_count_ptr());
+}
So,
Fixes: bdb438065890 ("sched: Extract the basic add/sub preempt_count
modifiers")
--
Konstantin
next prev parent reply other threads:[~2015-07-15 12:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-15 9:52 [PATCH v2 1/3] drivers/xen/preempt: use need_resched() instead of should_resched() Konstantin Khlebnikov
2015-07-15 9:52 ` Konstantin Khlebnikov
2015-07-15 9:52 ` [PATCH v2 2/3] KVM: PPC: Book3S HV: Use " Konstantin Khlebnikov
2015-07-15 9:52 ` Konstantin Khlebnikov
2015-07-15 9:52 ` [PATCH v2 3/3] sched/preempt: fix cond_resched_lock() and cond_resched_softirq() Konstantin Khlebnikov
2015-07-15 9:52 ` Konstantin Khlebnikov
2015-07-15 12:16 ` Eric Dumazet
2015-07-15 12:52 ` Konstantin Khlebnikov [this message]
2015-07-15 13:35 ` Peter Zijlstra
2015-07-20 13:41 ` [Xen-devel] [PATCH v2 1/3] drivers/xen/preempt: use need_resched() instead of should_resched() David Vrabel
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