Add cpu_relax() to various smpboot.c init loops.
Kept mb() since it's said to be required in some postings.
Tested on 2.6.17-mm1.
Signed-off-by: Andreas Mohr <[email protected]>
diff -urN linux-2.6.17-mm1.orig/arch/i386/kernel/smpboot.c linux-2.6.17-mm1.my/arch/i386/kernel/smpboot.c
--- linux-2.6.17-mm1.orig/arch/i386/kernel/smpboot.c 2006-06-21 14:28:15.000000000 +0200
+++ linux-2.6.17-mm1.my/arch/i386/kernel/smpboot.c 2006-06-21 14:43:24.000000000 +0200
@@ -251,8 +251,10 @@
/*
* all APs synchronize but they loop on '== num_cpus'
*/
- while (atomic_read(&tsc_count_start) != num_booting_cpus()-1)
+ while (atomic_read(&tsc_count_start) != num_booting_cpus()-1) {
+ cpu_relax();
mb();
+ }
atomic_set(&tsc_count_stop, 0);
wmb();
/*
@@ -270,8 +272,10 @@
/*
* Wait for all APs to leave the synchronization point:
*/
- while (atomic_read(&tsc_count_stop) != num_booting_cpus()-1)
+ while (atomic_read(&tsc_count_stop) != num_booting_cpus()-1) {
+ cpu_relax();
mb();
+ }
atomic_set(&tsc_count_start, 0);
wmb();
atomic_inc(&tsc_count_stop);
@@ -328,19 +332,27 @@
* 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();
+ mb();
+ }
for (i = 0; i < NR_LOOPS; i++) {
atomic_inc(&tsc_count_start);
- while (atomic_read(&tsc_count_start) != num_booting_cpus())
+ while (atomic_read(&tsc_count_start) != num_booting_cpus()) {
+ cpu_relax();
mb();
+ }
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();
+ mb();
+ }
}
}
#undef NR_LOOPS
@@ -1446,8 +1458,10 @@
per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
/* Unleash the CPU! */
cpu_set(cpu, smp_commenced_mask);
- while (!cpu_isset(cpu, cpu_online_map))
+ while (!cpu_isset(cpu, cpu_online_map)) {
+ cpu_relax();
mb();
+ }
return 0;
}
-
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