x86/mm: Fix RCU splat from new TLB tracepoints

Dave Jones reported seeing a bug from one of my TLB tracepoints:

        http://lkml.kernel.org/r/20140806181801.GA4605@redhat.com

According to Paul McKenney, the right way to fix this is adding
an _rcuidle suffix to the tracepoint.

        http://lkml.kernel.org/r/20140807065055.GA5821@linux.vnet.ibm.com

This patch does just that.

Reported-by: Dave Jones <davej@redhat.com>,
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140807175841.5C92D878@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 1fe33987de027f73c2997960198978a557bb1027..98b7976d44afecd5c343b982a7d6a478f32b1a83 100644 (file)
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -49,7 +49,13 @@ void leave_mm(int cpu)
        if (cpumask_test_cpu(cpu, mm_cpumask(active_mm))) {
                cpumask_clear_cpu(cpu, mm_cpumask(active_mm));
                load_cr3(swapper_pg_dir);
-               trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
+               /*
+                * This gets called in the idle path where RCU
+                * functions differently.  Tracing normally
+                * uses RCU, so we have to call the tracepoint
+                * specially here.
+                */
+               trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
        }
 }
 EXPORT_SYMBOL_GPL(leave_mm);