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| author | Wang YanQing <udknight@gmail.com> | 2013-01-26 15:53:57 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-02-03 18:21:38 -0600 |
| commit | d915fe310d9edbc349c36d0cef1b5dd0da6b067c (patch) | |
| tree | 54be4d4a1ecb40793bc65b5850ee6e79ed5c897b | |
| parent | 95675e4004fde70caaf119a9cb7ff489f3f0a069 (diff) | |
| download | lwn-d915fe310d9edbc349c36d0cef1b5dd0da6b067c.tar.gz lwn-d915fe310d9edbc349c36d0cef1b5dd0da6b067c.zip | |
smp: Fix SMP function call empty cpu mask race
commit f44310b98ddb7f0d06550d73ed67df5865e3eda5 upstream.
I get the following warning every day with v3.7, once or
twice a day:
[ 2235.186027] WARNING: at /mnt/sda7/kernel/linux/arch/x86/kernel/apic/ipi.c:109 default_send_IPI_mask_logical+0x2f/0xb8()
As explained by Linus as well:
|
| Once we've done the "list_add_rcu()" to add it to the
| queue, we can have (another) IPI to the target CPU that can
| now see it and clear the mask.
|
| So by the time we get to actually send the IPI, the mask might
| have been cleared by another IPI.
|
This patch also fixes a system hang problem, if the data->cpumask
gets cleared after passing this point:
if (WARN_ONCE(!mask, "empty IPI mask"))
return;
then the problem in commit 83d349f35e1a ("x86: don't send an IPI to
the empty set of CPU's") will happen again.
Signed-off-by: Wang YanQing <udknight@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Jan Beulich <jbeulich@suse.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: peterz@infradead.org
Cc: mina86@mina86.org
Cc: srivatsa.bhat@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/20130126075357.GA3205@udknight
[ Tidied up the changelog and the comment in the code. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/smp.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/kernel/smp.c b/kernel/smp.c index fb67dfa8394e..38d9e033bbc3 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -31,6 +31,7 @@ struct call_function_data { struct call_single_data csd; atomic_t refs; cpumask_var_t cpumask; + cpumask_var_t cpumask_ipi; }; static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); @@ -54,6 +55,9 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, cpu_to_node(cpu))) return notifier_from_errno(-ENOMEM); + if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, + cpu_to_node(cpu))) + return notifier_from_errno(-ENOMEM); break; #ifdef CONFIG_HOTPLUG_CPU @@ -63,6 +67,7 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) case CPU_DEAD: case CPU_DEAD_FROZEN: free_cpumask_var(cfd->cpumask); + free_cpumask_var(cfd->cpumask_ipi); break; #endif }; @@ -524,6 +529,12 @@ void smp_call_function_many(const struct cpumask *mask, return; } + /* + * After we put an entry into the list, data->cpumask + * may be cleared again when another CPU sends another IPI for + * a SMP function call, so data->cpumask will be zero. + */ + cpumask_copy(data->cpumask_ipi, data->cpumask); raw_spin_lock_irqsave(&call_function.lock, flags); /* * Place entry at the _HEAD_ of the list, so that any cpu still @@ -547,7 +558,7 @@ void smp_call_function_many(const struct cpumask *mask, smp_mb(); /* Send a message to all CPUs in the map */ - arch_send_call_function_ipi_mask(data->cpumask); + arch_send_call_function_ipi_mask(data->cpumask_ipi); /* Optionally wait for the CPUs to complete */ if (wait) |