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authorLinus Torvalds <torvalds@linux-foundation.org>2009-08-21 09:48:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-08-21 09:48:10 -0700
commitb04e6373d694e977c95ae0ae000e2c1e2cf92d73 (patch)
tree34bdbf7e11ba1beecff9b2a460f8cf775d1fe6d6
parentf4b0373b26567cafd421d91101852ed7a34e9e94 (diff)
x86: don't call '->send_IPI_mask()' with an empty mask
As noted in 83d349f35e1ae72268c5104dbf9ab2ae635425d4 ("x86: don't send an IPI to the empty set of CPU's"), some APIC's will be very unhappy with an empty destination mask. That commit added a WARN_ON() for that case, and avoided the resulting problem, but didn't fix the underlying reason for why those empty mask cases happened. This fixes that, by checking the result of 'cpumask_andnot()' of the current CPU actually has any other CPU's left in the set of CPU's to be sent a TLB flush, and not calling down to the IPI code if the mask is empty. The reason this started happening at all is that we started passing just the CPU mask pointers around in commit 4595f9620 ("x86: change flush_tlb_others to take a const struct cpumask"), and when we did that, the cpumask was no longer thread-local. Before that commit, flush_tlb_mm() used to create it's own copy of 'mm->cpu_vm_mask' and pass that copy down to the low-level flush routines after having tested that it was not empty. But after changing it to just pass down the CPU mask pointer, the lower level TLB flush routines would now get a pointer to that 'mm->cpu_vm_mask', and that could still change - and become empty - after the test due to other CPU's having flushed their own TLB's. See http://bugzilla.kernel.org/show_bug.cgi?id=13933 for details. Tested-by: Thomas Björnell <thomas.bjornell@gmail.com> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/x86/mm/tlb.c21
1 files changed, 10 insertions, 11 deletions
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 821e97017e95..c814e144a3f0 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -183,18 +183,17 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
f->flush_mm = mm;
f->flush_va = va;
- cpumask_andnot(to_cpumask(f->flush_cpumask),
- cpumask, cpumask_of(smp_processor_id()));
-
- /*
- * We have to send the IPI only to
- * CPUs affected.
- */
- apic->send_IPI_mask(to_cpumask(f->flush_cpumask),
- INVALIDATE_TLB_VECTOR_START + sender);
+ if (cpumask_andnot(to_cpumask(f->flush_cpumask), cpumask, cpumask_of(smp_processor_id()))) {
+ /*
+ * We have to send the IPI only to
+ * CPUs affected.
+ */
+ apic->send_IPI_mask(to_cpumask(f->flush_cpumask),
+ INVALIDATE_TLB_VECTOR_START + sender);
- while (!cpumask_empty(to_cpumask(f->flush_cpumask)))
- cpu_relax();
+ while (!cpumask_empty(to_cpumask(f->flush_cpumask)))
+ cpu_relax();
+ }
f->flush_mm = NULL;
f->flush_va = 0;