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authorIngo Molnar <mingo@elte.hu>2008-06-16 11:23:36 +0200
committerIngo Molnar <mingo@elte.hu>2008-06-16 11:23:36 +0200
commit766d02786ecd22932beeb9ca8bad6d8c5a552ef9 (patch)
treef6f2df0e35bbea914d1f4d12be6d02f128c73575 /arch/x86/lib/delay_32.c
parent906d882cacecd37ad2fdd03ed2a9b232bcb9507e (diff)
parent066519068ad2fbe98c7f45552b1f592903a9c8c8 (diff)
Merge branch 'linus' into core/rcutip-core-rcu-2008-06-16_09.23_Mon
Diffstat (limited to 'arch/x86/lib/delay_32.c')
-rw-r--r--arch/x86/lib/delay_32.c31
1 files changed, 27 insertions, 4 deletions
diff --git a/arch/x86/lib/delay_32.c b/arch/x86/lib/delay_32.c
index 4535e6d147ad..d710f2d167bb 100644
--- a/arch/x86/lib/delay_32.c
+++ b/arch/x86/lib/delay_32.c
@@ -44,13 +44,36 @@ static void delay_loop(unsigned long loops)
static void delay_tsc(unsigned long loops)
{
unsigned long bclock, now;
+ int cpu;
- preempt_disable(); /* TSC's are per-cpu */
+ preempt_disable();
+ cpu = smp_processor_id();
rdtscl(bclock);
- do {
- rep_nop();
+ for (;;) {
rdtscl(now);
- } while ((now-bclock) < loops);
+ if ((now - bclock) >= loops)
+ break;
+
+ /* Allow RT tasks to run */
+ preempt_enable();
+ rep_nop();
+ preempt_disable();
+
+ /*
+ * It is possible that we moved to another CPU, and
+ * since TSC's are per-cpu we need to calculate
+ * that. The delay must guarantee that we wait "at
+ * least" the amount of time. Being moved to another
+ * CPU could make the wait longer but we just need to
+ * make sure we waited long enough. Rebalance the
+ * counter for this CPU.
+ */
+ if (unlikely(cpu != smp_processor_id())) {
+ loops -= (now - bclock);
+ cpu = smp_processor_id();
+ rdtscl(bclock);
+ }
+ }
preempt_enable();
}