diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/ext_idle.c | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c index 7174e1c1a392..537c6992bb63 100644 --- a/kernel/sched/ext_idle.c +++ b/kernel/sched/ext_idle.c @@ -856,6 +856,32 @@ static bool check_builtin_idle_enabled(void) return false; } +/* + * Determine whether @p is a migration-disabled task in the context of BPF + * code. + * + * We can't simply check whether @p->migration_disabled is set in a + * sched_ext callback, because migration is always disabled for the current + * task while running BPF code. + * + * The prolog (__bpf_prog_enter) and epilog (__bpf_prog_exit) respectively + * disable and re-enable migration. For this reason, the current task + * inside a sched_ext callback is always a migration-disabled task. + * + * Therefore, when @p->migration_disabled == 1, check whether @p is the + * current task or not: if it is, then migration was not disabled before + * entering the callback, otherwise migration was disabled. + * + * Returns true if @p is migration-disabled, false otherwise. + */ +static bool is_bpf_migration_disabled(const struct task_struct *p) +{ + if (p->migration_disabled == 1) + return p != current; + else + return p->migration_disabled; +} + static s32 select_cpu_from_kfunc(struct task_struct *p, s32 prev_cpu, u64 wake_flags, const struct cpumask *allowed, u64 flags) { @@ -898,7 +924,7 @@ static s32 select_cpu_from_kfunc(struct task_struct *p, s32 prev_cpu, u64 wake_f * selection optimizations and simply check whether the previously * used CPU is idle and within the allowed cpumask. */ - if (p->nr_cpus_allowed == 1 || is_migration_disabled(p)) { + if (p->nr_cpus_allowed == 1 || is_bpf_migration_disabled(p)) { if (cpumask_test_cpu(prev_cpu, allowed ?: p->cpus_ptr) && scx_idle_test_and_clear_cpu(prev_cpu)) cpu = prev_cpu; |