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x86/irq: Use proper locking in check_irq_vectors_for_cpu_disable() 

It's unsafe to examine fields in the irq descriptor w/o holding the
descriptor lock. Add proper locking.

While at it add a comment why the vector check can run lock less

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: xiao jin <jin.xiao@intel.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Link: http://lkml.kernel.org/r/20150705171102.236544164@linutronix.de
This commit is contained in:
Thomas Gleixner 2015-07-05 17:12:33 +00:00
parent 5a3f75e3f0
commit cbb24dc761
1 changed files with 12 additions and 1 deletions
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13
arch/x86/kernel/irq.c
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@ -347,14 +347,22 @@ int check_irq_vectors_for_cpu_disable(void)
if (!desc) if (!desc)
continue; continue;
/*
* Protect against concurrent action removal,
* affinity changes etc.
*/
raw_spin_lock(&desc->lock);
data = irq_desc_get_irq_data(desc); data = irq_desc_get_irq_data(desc);
cpumask_copy(&affinity_new, data->affinity); cpumask_copy(&affinity_new, data->affinity);
cpumask_clear_cpu(this_cpu, &affinity_new); cpumask_clear_cpu(this_cpu, &affinity_new);
/* Do not count inactive or per-cpu irqs. */ /* Do not count inactive or per-cpu irqs. */
if (!irq_has_action(irq) || irqd_is_per_cpu(data)) if (!irq_has_action(irq) || irqd_is_per_cpu(data)) {
raw_spin_unlock(&desc->lock);
continue; continue;
}
raw_spin_unlock(&desc->lock);
/* /*
* A single irq may be mapped to multiple * A single irq may be mapped to multiple
* cpu's vector_irq[] (for example IOAPIC cluster * cpu's vector_irq[] (for example IOAPIC cluster
@ -385,6 +393,9 @@ int check_irq_vectors_for_cpu_disable(void)
* vector. If the vector is marked in the used vectors * vector. If the vector is marked in the used vectors
* bitmap or an irq is assigned to it, we don't count * bitmap or an irq is assigned to it, we don't count
* it as available. * it as available.
*
* As this is an inaccurate snapshot anyway, we can do
* this w/o holding vector_lock.
*/ */
for (vector = FIRST_EXTERNAL_VECTOR; for (vector = FIRST_EXTERNAL_VECTOR;
vector < first_system_vector; vector++) { vector < first_system_vector; vector++) {