[PATCH] cpu_relax(): smpboot.c
Add cpu_relax() to various smpboot.c init loops. cpu_relax() always implies a
barrier (according to Arjan), so remove those as well.
Signed-off-by: Andreas Mohr <andi@lisas.de>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 825b2b4..bd0ca5c 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -257,7 +257,7 @@
* all APs synchronize but they loop on '== num_cpus'
*/
while (atomic_read(&tsc_count_start) != num_booting_cpus()-1)
- mb();
+ cpu_relax();
atomic_set(&tsc_count_stop, 0);
wmb();
/*
@@ -276,7 +276,7 @@
* Wait for all APs to leave the synchronization point:
*/
while (atomic_read(&tsc_count_stop) != num_booting_cpus()-1)
- mb();
+ cpu_relax();
atomic_set(&tsc_count_start, 0);
wmb();
atomic_inc(&tsc_count_stop);
@@ -333,19 +333,21 @@
* this gets called, so we first wait for the BP to
* finish SMP initialization:
*/
- while (!atomic_read(&tsc_start_flag)) mb();
+ while (!atomic_read(&tsc_start_flag))
+ cpu_relax();
for (i = 0; i < NR_LOOPS; i++) {
atomic_inc(&tsc_count_start);
while (atomic_read(&tsc_count_start) != num_booting_cpus())
- mb();
+ cpu_relax();
rdtscll(tsc_values[smp_processor_id()]);
if (i == NR_LOOPS-1)
write_tsc(0, 0);
atomic_inc(&tsc_count_stop);
- while (atomic_read(&tsc_count_stop) != num_booting_cpus()) mb();
+ while (atomic_read(&tsc_count_stop) != num_booting_cpus())
+ cpu_relax();
}
}
#undef NR_LOOPS
@@ -1433,7 +1435,7 @@
/* Unleash the CPU! */
cpu_set(cpu, smp_commenced_mask);
while (!cpu_isset(cpu, cpu_online_map))
- mb();
+ cpu_relax();
return 0;
}