From 6f25f3986af0353b0bdc220f79b89c997d0ceda4 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Tue, 28 Mar 2006 13:29:26 -0800 Subject: [PATCH] [SPARC64]: Make tsb_sync() mm comparison more precise. switch_mm() changes the mm state and does a tsb_context_switch() first, then we do the cpu register state switch which changes current_thread_info() and current(). So it's safer to check the PGD physical address stored in the trap block (which will be updated by the tsb_context_switch() in switch_mm()) than current->active_mm. Technically we should never run here in between those two updates, because interrupts are disabled during the entire context switch operation. But some day we might like to leave interrupts enabled during the context switch and this change allows that to happen without any surprises. Signed-off-by: David S. Miller --- arch/sparc64/kernel/smp.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/sparc64/kernel/smp.c b/arch/sparc64/kernel/smp.c index 7dc28a484268..8175a6968c6b 100644 --- a/arch/sparc64/kernel/smp.c +++ b/arch/sparc64/kernel/smp.c @@ -830,9 +830,16 @@ void smp_call_function_client(int irq, struct pt_regs *regs) static void tsb_sync(void *info) { + struct trap_per_cpu *tp = &trap_block[raw_smp_processor_id()]; struct mm_struct *mm = info; - if (current->active_mm == mm) + /* It is not valid to test "currrent->active_mm == mm" here. + * + * The value of "current" is not changed atomically with + * switch_mm(). But that's OK, we just need to check the + * current cpu's trap block PGD physical address. + */ + if (tp->pgd_paddr == __pa(mm->pgd)) tsb_context_switch(mm); }