From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking Date: Thu, 1 Sep 2011 17:55:01 -0700 Message-ID: <38bb37e15f6e5056d5238adac945bc1837a996ec.1314922370.git.jeremy.fitzhardinge@citrix.com> References: Return-path: In-Reply-To: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org To: "H. Peter Anvin" Cc: Linus Torvalds , Peter Zijlstra , Ingo Molnar , the arch/x86 maintainers , Linux Kernel Mailing List , Nick Piggin , Avi Kivity , Marcelo Tosatti , KVM , Andi Kleen , Xen Devel , Jeremy Fitzhardinge List-Id: xen-devel@lists.xenproject.org From: Jeremy Fitzhardinge We need to make sure interrupts are disabled while we're relying on the contents of the per-cpu lock_waiting values, otherwise an interrupt handler could come in, try to take some other lock, block, and overwrite our values. Signed-off-by: Jeremy Fitzhardinge --- arch/x86/xen/spinlock.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index 4c46144..2ed5d05 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -98,6 +98,7 @@ static void xen_lock_spinning(struct arch_spinlock *lock, unsigned want) struct xen_lock_waiting *w = &__get_cpu_var(lock_waiting); int cpu = smp_processor_id(); u64 start; + unsigned long flags; /* If kicker interrupts not initialized yet, just spin */ if (irq == -1) @@ -105,6 +106,10 @@ static void xen_lock_spinning(struct arch_spinlock *lock, unsigned want) start = spin_time_start(); + /* Make sure interrupts are disabled to ensure that these + per-cpu values are not overwritten. */ + local_irq_save(flags); + w->want = want; w->lock = lock; @@ -139,6 +144,9 @@ static void xen_lock_spinning(struct arch_spinlock *lock, unsigned want) out: cpumask_clear_cpu(cpu, &waiting_cpus); w->lock = NULL; + + local_irq_restore(flags); + spin_time_accum_blocked(start); } PV_CALLEE_SAVE_REGS_THUNK(xen_lock_spinning); -- 1.7.6