diff options
| author | Andy Lutomirski <luto@kernel.org> | 2017-06-29 08:53:13 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-06-30 10:12:35 +0200 |
| commit | bc0d5a89fbe3c83ac45438d7ba88309f4713615d (patch) | |
| tree | 5c130627575ae6a34521daec569e87dec95b8eb9 /arch/x86/mm/tlb.c | |
| parent | a24261d70e00e4ce03cf45bbf18398f52a7b9229 (diff) | |
x86/mm: Don't reenter flush_tlb_func_common()
It was historically possible to have two concurrent TLB flushes
targetting the same CPU: one initiated locally and one initiated
remotely. This can now cause an OOPS in leave_mm() at
arch/x86/mm/tlb.c:47:
if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
BUG();
with this call trace:
flush_tlb_func_local arch/x86/mm/tlb.c:239 [inline]
flush_tlb_mm_range+0x26d/0x370 arch/x86/mm/tlb.c:317
Without reentrancy, this OOPS is impossible: leave_mm() is only
called if we're not in TLBSTATE_OK, but then we're unexpectedly
in TLBSTATE_OK in leave_mm().
This can be caused by flush_tlb_func_remote() happening between
the two checks and calling leave_mm(), resulting in two consecutive
leave_mm() calls on the same CPU with no intervening switch_mm()
calls.
We never saw this OOPS before because the old leave_mm()
implementation didn't put us back in TLBSTATE_OK, so the assertion
didn't fire.
Nadav noticed the reentrancy issue in a different context, but
neither of us realized that it caused a problem yet.
Reported-by: Levin, Alexander (Sasha Levin) <alexander.levin@verizon.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Nadav Amit <nadav.amit@gmail.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Fixes: 3d28ebceaffa ("x86/mm: Rework lazy TLB to track the actual loaded mm")
Link: http://lkml.kernel.org/r/855acf733268d521c9f2e191faee2dcc23a29729.1498751203.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/mm/tlb.c')
| -rw-r--r-- | arch/x86/mm/tlb.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index b2485d69f7c2..1cc47838d1e8 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -192,6 +192,9 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, static void flush_tlb_func_common(const struct flush_tlb_info *f, bool local, enum tlb_flush_reason reason) { + /* This code cannot presently handle being reentered. */ + VM_WARN_ON(!irqs_disabled()); + if (this_cpu_read(cpu_tlbstate.state) != TLBSTATE_OK) { leave_mm(smp_processor_id()); return; @@ -297,8 +300,13 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start, info.end = TLB_FLUSH_ALL; } - if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) + if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) { + VM_WARN_ON(irqs_disabled()); + local_irq_disable(); flush_tlb_func_local(&info, TLB_LOCAL_MM_SHOOTDOWN); + local_irq_enable(); + } + if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids) flush_tlb_others(mm_cpumask(mm), &info); put_cpu(); @@ -354,8 +362,13 @@ void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch) int cpu = get_cpu(); - if (cpumask_test_cpu(cpu, &batch->cpumask)) + if (cpumask_test_cpu(cpu, &batch->cpumask)) { + VM_WARN_ON(irqs_disabled()); + local_irq_disable(); flush_tlb_func_local(&info, TLB_LOCAL_SHOOTDOWN); + local_irq_enable(); + } + if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids) flush_tlb_others(&batch->cpumask, &info); cpumask_clear(&batch->cpumask); |