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x86: Simplify cpu_idle_wait
This patch also resolves hangs on boot:
http://lkml.org/lkml/2008/2/23/263
http://bugzilla.kernel.org/show_bug.cgi?id=10093
The bug was causing once-in-few-reboots 10-15 sec wait during boot on
certain laptops.
Earlier commit 40d6a14662
added
smp_call_function in cpu_idle_wait() to kick cpus that are in tickless
idle. Looking at cpu_idle_wait code at that time, code seemed to be
over-engineered for a case which is rarely used (while changing idle
handler).
Below is a simplified version of cpu_idle_wait, which just makes a dummy
smp_call_function to all cpus, to make them come out of old idle handler
and start using the new idle handler. It eliminates code in the idle
loop to handle cpu_idle_wait.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
a1e58bbdc9
commit
783e391b7b
@ -82,7 +82,6 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
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*/
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void (*pm_idle)(void);
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EXPORT_SYMBOL(pm_idle);
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static DEFINE_PER_CPU(unsigned int, cpu_idle_state);
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void disable_hlt(void)
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{
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@ -190,9 +189,6 @@ void cpu_idle(void)
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while (!need_resched()) {
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void (*idle)(void);
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if (__get_cpu_var(cpu_idle_state))
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__get_cpu_var(cpu_idle_state) = 0;
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check_pgt_cache();
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rmb();
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idle = pm_idle;
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@ -220,40 +216,19 @@ static void do_nothing(void *unused)
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{
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}
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/*
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* cpu_idle_wait - Used to ensure that all the CPUs discard old value of
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* pm_idle and update to new pm_idle value. Required while changing pm_idle
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* handler on SMP systems.
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*
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* Caller must have changed pm_idle to the new value before the call. Old
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* pm_idle value will not be used by any CPU after the return of this function.
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*/
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void cpu_idle_wait(void)
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{
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unsigned int cpu, this_cpu = get_cpu();
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cpumask_t map, tmp = current->cpus_allowed;
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set_cpus_allowed(current, cpumask_of_cpu(this_cpu));
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put_cpu();
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cpus_clear(map);
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for_each_online_cpu(cpu) {
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per_cpu(cpu_idle_state, cpu) = 1;
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cpu_set(cpu, map);
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}
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__get_cpu_var(cpu_idle_state) = 0;
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wmb();
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do {
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ssleep(1);
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for_each_online_cpu(cpu) {
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if (cpu_isset(cpu, map) && !per_cpu(cpu_idle_state, cpu))
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cpu_clear(cpu, map);
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}
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cpus_and(map, map, cpu_online_map);
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/*
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* We waited 1 sec, if a CPU still did not call idle
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* it may be because it is in idle and not waking up
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* because it has nothing to do.
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* Give all the remaining CPUS a kick.
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*/
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smp_call_function_mask(map, do_nothing, NULL, 0);
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} while (!cpus_empty(map));
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set_cpus_allowed(current, tmp);
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smp_mb();
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/* kick all the CPUs so that they exit out of pm_idle */
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smp_call_function(do_nothing, NULL, 0, 1);
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}
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EXPORT_SYMBOL_GPL(cpu_idle_wait);
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@ -63,7 +63,6 @@ EXPORT_SYMBOL(boot_option_idle_override);
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*/
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void (*pm_idle)(void);
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EXPORT_SYMBOL(pm_idle);
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static DEFINE_PER_CPU(unsigned int, cpu_idle_state);
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static ATOMIC_NOTIFIER_HEAD(idle_notifier);
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@ -173,9 +172,6 @@ void cpu_idle(void)
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while (!need_resched()) {
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void (*idle)(void);
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if (__get_cpu_var(cpu_idle_state))
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__get_cpu_var(cpu_idle_state) = 0;
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rmb();
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idle = pm_idle;
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if (!idle)
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@ -207,40 +203,19 @@ static void do_nothing(void *unused)
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{
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}
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/*
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* cpu_idle_wait - Used to ensure that all the CPUs discard old value of
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* pm_idle and update to new pm_idle value. Required while changing pm_idle
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* handler on SMP systems.
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*
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* Caller must have changed pm_idle to the new value before the call. Old
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* pm_idle value will not be used by any CPU after the return of this function.
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*/
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void cpu_idle_wait(void)
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{
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unsigned int cpu, this_cpu = get_cpu();
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cpumask_t map, tmp = current->cpus_allowed;
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set_cpus_allowed(current, cpumask_of_cpu(this_cpu));
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put_cpu();
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cpus_clear(map);
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for_each_online_cpu(cpu) {
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per_cpu(cpu_idle_state, cpu) = 1;
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cpu_set(cpu, map);
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}
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__get_cpu_var(cpu_idle_state) = 0;
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wmb();
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do {
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ssleep(1);
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for_each_online_cpu(cpu) {
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if (cpu_isset(cpu, map) && !per_cpu(cpu_idle_state, cpu))
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cpu_clear(cpu, map);
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}
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cpus_and(map, map, cpu_online_map);
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/*
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* We waited 1 sec, if a CPU still did not call idle
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* it may be because it is in idle and not waking up
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* because it has nothing to do.
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* Give all the remaining CPUS a kick.
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*/
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smp_call_function_mask(map, do_nothing, 0, 0);
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} while (!cpus_empty(map));
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set_cpus_allowed(current, tmp);
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smp_mb();
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/* kick all the CPUs so that they exit out of pm_idle */
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smp_call_function(do_nothing, NULL, 0, 1);
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}
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EXPORT_SYMBOL_GPL(cpu_idle_wait);
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