diff options
Diffstat (limited to 'debian/patches-rt/0290-sched-Simplify-migration_cpu_stop.patch')
| -rw-r--r-- | debian/patches-rt/0290-sched-Simplify-migration_cpu_stop.patch | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/debian/patches-rt/0290-sched-Simplify-migration_cpu_stop.patch b/debian/patches-rt/0290-sched-Simplify-migration_cpu_stop.patch new file mode 100644 index 000000000..4d0841707 --- /dev/null +++ b/debian/patches-rt/0290-sched-Simplify-migration_cpu_stop.patch @@ -0,0 +1,142 @@ +From 4f468832c2a5bb5c0bb23b453038ff4fed722061 Mon Sep 17 00:00:00 2001 +From: Peter Zijlstra <peterz@infradead.org> +Date: Tue, 8 Jun 2021 00:37:31 -0400 +Subject: [PATCH 290/323] sched: Simplify migration_cpu_stop() +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz + +commit c20cf065d4a619d394d23290093b1002e27dff86 upstream. + +When affine_move_task() issues a migration_cpu_stop(), the purpose of +that function is to complete that @pending, not any random other +p->migration_pending that might have gotten installed since. + +This realization much simplifies migration_cpu_stop() and allows +further necessary steps to fix all this as it provides the guarantee +that @pending's stopper will complete @pending (and not some random +other @pending). + +Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") +Cc: stable@kernel.org +Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> +Signed-off-by: Ingo Molnar <mingo@kernel.org> +Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> +Link: https://lkml.kernel.org/r/20210224131355.430014682@infradead.org +Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> +Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> +--- + kernel/sched/core.c | 56 +++++++-------------------------------------- + 1 file changed, 8 insertions(+), 48 deletions(-) + +diff --git a/kernel/sched/core.c b/kernel/sched/core.c +index df9c4c3838c0..31fa925852e5 100644 +--- a/kernel/sched/core.c ++++ b/kernel/sched/core.c +@@ -1950,8 +1950,8 @@ static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf, + */ + static int migration_cpu_stop(void *data) + { +- struct set_affinity_pending *pending; + struct migration_arg *arg = data; ++ struct set_affinity_pending *pending = arg->pending; + struct task_struct *p = arg->task; + int dest_cpu = arg->dest_cpu; + struct rq *rq = this_rq(); +@@ -1973,25 +1973,6 @@ static int migration_cpu_stop(void *data) + raw_spin_lock(&p->pi_lock); + rq_lock(rq, &rf); + +- pending = p->migration_pending; +- if (pending && !arg->pending) { +- /* +- * This happens from sched_exec() and migrate_task_to(), +- * neither of them care about pending and just want a task to +- * maybe move about. +- * +- * Even if there is a pending, we can ignore it, since +- * affine_move_task() will have it's own stop_work's in flight +- * which will manage the completion. +- * +- * Notably, pending doesn't need to match arg->pending. This can +- * happen when tripple concurrent affine_move_task() first sets +- * pending, then clears pending and eventually sets another +- * pending. +- */ +- pending = NULL; +- } +- + /* + * If task_rq(p) != rq, it cannot be migrated here, because we're + * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because +@@ -2002,31 +1983,20 @@ static int migration_cpu_stop(void *data) + goto out; + + if (pending) { +- p->migration_pending = NULL; ++ if (p->migration_pending == pending) ++ p->migration_pending = NULL; + complete = true; + } + +- /* migrate_enable() -- we must not race against SCA */ +- if (dest_cpu < 0) { +- /* +- * When this was migrate_enable() but we no longer +- * have a @pending, a concurrent SCA 'fixed' things +- * and we should be valid again. Nothing to do. +- */ +- if (!pending) { +- WARN_ON_ONCE(!cpumask_test_cpu(task_cpu(p), &p->cpus_mask)); +- goto out; +- } +- ++ if (dest_cpu < 0) + dest_cpu = cpumask_any_distribute(&p->cpus_mask); +- } + + if (task_on_rq_queued(p)) + rq = __migrate_task(rq, &rf, p, dest_cpu); + else + p->wake_cpu = dest_cpu; + +- } else if (dest_cpu < 0 || pending) { ++ } else if (pending) { + /* + * This happens when we get migrated between migrate_enable()'s + * preempt_enable() and scheduling the stopper task. At that +@@ -2041,22 +2011,13 @@ static int migration_cpu_stop(void *data) + * ->pi_lock, so the allowed mask is stable - if it got + * somewhere allowed, we're done. + */ +- if (pending && cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) { +- p->migration_pending = NULL; ++ if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) { ++ if (p->migration_pending == pending) ++ p->migration_pending = NULL; + complete = true; + goto out; + } + +- /* +- * When this was migrate_enable() but we no longer have an +- * @pending, a concurrent SCA 'fixed' things and we should be +- * valid again. Nothing to do. +- */ +- if (!pending) { +- WARN_ON_ONCE(!cpumask_test_cpu(task_cpu(p), &p->cpus_mask)); +- goto out; +- } +- + /* + * When migrate_enable() hits a rq mis-match we can't reliably + * determine is_migration_disabled() and so have to chase after +@@ -2074,7 +2035,6 @@ static int migration_cpu_stop(void *data) + complete_all(&pending->done); + + /* For pending->{arg,stop_work} */ +- pending = arg->pending; + if (pending && refcount_dec_and_test(&pending->refs)) + wake_up_var(&pending->refs); + +-- +2.43.0 + |