[IA64] eliminate race condition in smp_flush_tlb_mm

A race condition exists within smp_call_function_many() when called from
smp_flush_tlb_mm().  On rare occasions the cpu_vm_mask can be cleared
while smp_call_function_many is executing, occasionally resulting in a
hung process.

Make a copy of the mask prior to calling smp_call_function_many().

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/arch/ia64/kernel/smp.c b/arch/ia64/kernel/smp.c
index dabeefe..be450a3 100644 (file)
--- a/arch/ia64/kernel/smp.c
+++ b/arch/ia64/kernel/smp.c
@@ -293,6 +293,7 @@ smp_flush_tlb_all (void)
 void
 smp_flush_tlb_mm (struct mm_struct *mm)
 {
+       cpumask_var_t cpus;
        preempt_disable();
        /* this happens for the common case of a single-threaded fork():  */
        if (likely(mm == current->active_mm && atomic_read(&mm->mm_users) == 1))
@@ -301,9 +302,15 @@ smp_flush_tlb_mm (struct mm_struct *mm)
                preempt_enable();
                return;
        }
-
-       smp_call_function_many(mm_cpumask(mm),
-               (void (*)(void *))local_finish_flush_tlb_mm, mm, 1);
+       if (!alloc_cpumask_var(&cpus, GFP_ATOMIC)) {
+               smp_call_function((void (*)(void *))local_finish_flush_tlb_mm,
+                       mm, 1);
+       } else {
+               cpumask_copy(cpus, mm_cpumask(mm));
+               smp_call_function_many(cpus,
+                       (void (*)(void *))local_finish_flush_tlb_mm, mm, 1);
+               free_cpumask_var(cpus);
+       }
        local_irq_disable();
        local_finish_flush_tlb_mm(mm);
        local_irq_enable();