[PATCH] Fix TIF_POLLING_NRFLAG in ACPI idle routines

Commit 64c7c8f88559624abdbe12b5da6502e8879f8d28 broke the ACPI C2 and C3
sleep states, because it left TIF_POLLING_NRFLAG active even though
those states do not actually poll the reschedule flag at all.  As a
result, the CPU wouldn't get sent an IPI when it was to be woken up, and
would only notice that it had runnable processes on the next timer tick.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 14 insertions, 7 deletions

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 83fd1b6c10c4..acd875e0caca 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -169,15 +169,11 @@ acpi_processor_power_activate(struct acpi_processor *pr,
 
 static void acpi_safe_halt(void)
 {
-        int polling = test_thread_flag(TIF_POLLING_NRFLAG);
-        if (polling) {
-                clear_thread_flag(TIF_POLLING_NRFLAG);
-                smp_mb__after_clear_bit();
-        }
+        clear_thread_flag(TIF_POLLING_NRFLAG);
+        smp_mb__after_clear_bit();
         if (!need_resched())
                 safe_halt();
-        if (polling)
-                set_thread_flag(TIF_POLLING_NRFLAG);
+        set_thread_flag(TIF_POLLING_NRFLAG);
 }
 
 static atomic_t c3_cpu_count;
@@ -295,6 +291,15 @@ static void acpi_processor_idle(void)
          * ------
          * Invoke the current Cx state to put the processor to sleep.
          */
+        if (cx->type == ACPI_STATE_C2 || cx->type == ACPI_STATE_C3) {
+                clear_thread_flag(TIF_POLLING_NRFLAG);
+                smp_mb__after_clear_bit();
+                if (need_resched()) {
+                        set_thread_flag(TIF_POLLING_NRFLAG);
+                        return;
+                }
+        }
+
         switch (cx->type) {
 
         case ACPI_STATE_C1:
@@ -327,6 +332,7 @@ static void acpi_processor_idle(void)
                 t2 = inl(acpi_fadt.xpm_tmr_blk.address);
                 /* Re-enable interrupts */
                 local_irq_enable();
+                set_thread_flag(TIF_POLLING_NRFLAG);
                 /* Compute time (ticks) that we were actually asleep */
                 sleep_ticks =
                     ticks_elapsed(t1, t2) - cx->latency_ticks - C2_OVERHEAD;
@@ -366,6 +372,7 @@ static void acpi_processor_idle(void)
 
                 /* Re-enable interrupts */
                 local_irq_enable();
+                set_thread_flag(TIF_POLLING_NRFLAG);
                 /* Compute time (ticks) that we were actually asleep */
                 sleep_ticks =
                     ticks_elapsed(t1, t2) - cx->latency_ticks - C3_OVERHEAD;