smp: Fix SMP function call empty cpu mask race
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
Cc: <stable@kernel.org>
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>
diff --git a/kernel/smp.c b/kernel/smp.c
index 29dd40a..69f38bd 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -33,6 +33,7 @@
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);
@@ -56,6 +57,9 @@
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
@@ -65,6 +69,7 @@
case CPU_DEAD:
case CPU_DEAD_FROZEN:
free_cpumask_var(cfd->cpumask);
+ free_cpumask_var(cfd->cpumask_ipi);
break;
#endif
};
@@ -526,6 +531,12 @@
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
@@ -549,7 +560,7 @@
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)
