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sched/walt: correct return value for walt_pause/resume_cpus()

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It is possible that pause/resume of CPUs can fail, but
walt_pause/resume_cpus() always returns zero which turns
even failures into success. This would leave clients go
into bad state in case of failures. To avoid such issues
separate out ref count updates and clearing pause/resume
masks (when the CPUs are already paused/resumed cases) and
rearrange the code appropriately to make sure ref counting
is properly handled in case of errors.

Change-Id: I284752bf9372cada30a2b648f1c9c54446923117
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>
This commit is contained in:
Satya Durga Srinivasu Prabhala 2021-06-18 02:42:26 -07:00 committed by Rishabh Bhatnagar
parent 92074a3d0d
commit 8ce4bfae2f
1 changed files with 20 additions and 27 deletions
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47
kernel/sched/walt/walt_pause.c
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@ -16,33 +16,30 @@ struct pause_cpu_state {
static DEFINE_PER_CPU(struct pause_cpu_state, pause_state);
/* increment ref count for cpus in passed mask */
static void inc_ref_counts(struct cpumask *cpus)
/* increment/decrement ref count for cpus in pause/resume mask */
static void update_ref_counts(struct cpumask *cpus, bool pause)
{
int cpu;
struct pause_cpu_state *pause_cpu_state;
for_each_cpu(cpu, cpus) {
pause_cpu_state = per_cpu_ptr(&pause_state, cpu);
if (pause_cpu_state->ref_count)
cpumask_clear_cpu(cpu, cpus);
pause_cpu_state->ref_count++;
if (pause)
pause_cpu_state->ref_count++;
else {
WARN_ON_ONCE(pause_cpu_state->ref_count == 0);
pause_cpu_state->ref_count--;
}
}
}
/*
* decrement ref count for cpus in passed mask
* updates the cpus to include only cpus ready to be unpaused
*/
static void dec_test_ref_counts(struct cpumask *cpus)
static void update_pause_resume_cpus(struct cpumask *cpus)
{
int cpu;
struct pause_cpu_state *pause_cpu_state;
for_each_cpu(cpu, cpus) {
pause_cpu_state = per_cpu_ptr(&pause_state, cpu);
WARN_ON_ONCE(pause_cpu_state->ref_count == 0);
pause_cpu_state->ref_count--;
if (pause_cpu_state->ref_count)
cpumask_clear_cpu(cpu, cpus);
}
@ -57,26 +54,24 @@ int walt_pause_cpus(struct cpumask *cpus)
mutex_lock(&pause_lock);
cpumask_copy(&requested_cpus, cpus);
inc_ref_counts(cpus);
update_pause_resume_cpus(cpus);
/*
* Add ref counts for all cpus in mask, but
* only actually pause online CPUs
*/
cpumask_and(cpus, cpus, cpu_online_mask);
if (cpumask_empty(cpus))
if (cpumask_empty(cpus)) {
update_ref_counts(&requested_cpus, true);
goto unlock;
}
ret = pause_cpus(cpus);
if (ret < 0) {
if (ret < 0)
printk_deferred("pause_cpus failure ret=%d cpus=%*pbl\n", ret,
cpumask_pr_args(&requested_cpus));
/* ref counts recorded, suppress failure */
ret = 0;
}
else
update_ref_counts(&requested_cpus, true);
unlock:
mutex_unlock(&pause_lock);
@ -92,22 +87,20 @@ int walt_resume_cpus(struct cpumask *cpus)
mutex_lock(&pause_lock);
cpumask_copy(&requested_cpus, cpus);
dec_test_ref_counts(cpus);
update_ref_counts(&requested_cpus, false);
update_pause_resume_cpus(cpus);
/* only actually resume online CPUs */
cpumask_and(cpus, cpus, cpu_online_mask);
if (cpumask_empty(cpus))
goto unlock;
ret = resume_cpus(cpus);
if (ret < 0) {
printk_deferred("resume_cpus failure ret=%d cpus=%*pbl\n", ret,
cpumask_pr_args(&requested_cpus));
/* ref counts recorded, suppress failure */
ret = 0;
/* restore/increment ref counts in case of error */
update_ref_counts(&requested_cpus, true);
}
unlock:
mutex_unlock(&pause_lock);