diff options
Diffstat (limited to 'debian/patches-rt/rt-Increase-decrease-the-nr-of-migratory-tasks-when-.patch')
| -rw-r--r-- | debian/patches-rt/rt-Increase-decrease-the-nr-of-migratory-tasks-when-.patch | 155 |
1 files changed, 0 insertions, 155 deletions
diff --git a/debian/patches-rt/rt-Increase-decrease-the-nr-of-migratory-tasks-when-.patch b/debian/patches-rt/rt-Increase-decrease-the-nr-of-migratory-tasks-when-.patch deleted file mode 100644 index 28c93480a..000000000 --- a/debian/patches-rt/rt-Increase-decrease-the-nr-of-migratory-tasks-when-.patch +++ /dev/null @@ -1,155 +0,0 @@ -From: Daniel Bristot de Oliveira <bristot@redhat.com> -Date: Mon, 26 Jun 2017 17:07:15 +0200 -Subject: rt: Increase/decrease the nr of migratory tasks when enabling/disabling migration -Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.17-rt9.tar.xz - -There is a problem in the migrate_disable()/enable() implementation -regarding the number of migratory tasks in the rt/dl RQs. The problem -is the following: - -When a task is attached to the rt runqueue, it is checked if it either -can run in more than one CPU, or if it is with migration disable. If -either check is true, the rt_rq->rt_nr_migratory counter is not -increased. The counter increases otherwise. - -When the task is detached, the same check is done. If either check is -true, the rt_rq->rt_nr_migratory counter is not decreased. The counter -decreases otherwise. The same check is done in the dl scheduler. - -One important thing is that, migrate disable/enable does not touch this -counter for tasks attached to the rt rq. So suppose the following chain -of events. - -Assumptions: -Task A is the only runnable task in A Task B runs on the CPU B -Task A runs on CFS (non-rt) Task B has RT priority -Thus, rt_nr_migratory is 0 B is running -Task A can run on all CPUS. - -Timeline: - CPU A/TASK A CPU B/TASK B -A takes the rt mutex X . -A disables migration . - . B tries to take the rt mutex X - . As it is held by A { - . A inherits the rt priority of B - . A is dequeued from CFS RQ of CPU A - . A is enqueued in the RT RQ of CPU A - . As migration is disabled - . rt_nr_migratory in A is not increased - . -A enables migration -A releases the rt mutex X { - A returns to its original priority - A ask to be dequeued from RT RQ { - As migration is now enabled and it can run on all CPUS { - rt_nr_migratory should be decreased - As rt_nr_migratory is 0, rt_nr_migratory under flows - } -} - -This variable is important because it notifies if there are more than one -runnable & migratory task in the runqueue. If there are more than one -tasks, the rt_rq is set as overloaded, and then tries to migrate some -tasks. This rule is important to keep the scheduler working conserving, -that is, in a system with M CPUs, the M highest priority tasks should be -running. - -As rt_nr_migratory is unsigned, it will become > 0, notifying that the -RQ is overloaded, activating pushing mechanism without need. - -This patch fixes this problem by decreasing/increasing the -rt/dl_nr_migratory in the migrate disable/enable operations. - -Reported-by: Pei Zhang <pezhang@redhat.com> -Reported-by: Luiz Capitulino <lcapitulino@redhat.com> -Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> -Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com> -Cc: Clark Williams <williams@redhat.com> -Cc: Luiz Capitulino <lcapitulino@redhat.com> -Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> -Cc: Thomas Gleixner <tglx@linutronix.de> -Cc: Steven Rostedt <rostedt@goodmis.org> -Cc: Peter Zijlstra <peterz@infradead.org> -Cc: Ingo Molnar <mingo@kernel.org> -Cc: LKML <linux-kernel@vger.kernel.org> -Cc: linux-rt-users <linux-rt-users@vger.kernel.org> -Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> ---- - kernel/sched/core.c | 49 ++++++++++++++++++++++++++++++++++++++++++++----- - 1 file changed, 44 insertions(+), 5 deletions(-) - ---- a/kernel/sched/core.c -+++ b/kernel/sched/core.c -@@ -7152,6 +7152,47 @@ const u32 sched_prio_to_wmult[40] = { - - #if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_SMP) - -+static inline void -+update_nr_migratory(struct task_struct *p, long delta) -+{ -+ if (unlikely((p->sched_class == &rt_sched_class || -+ p->sched_class == &dl_sched_class) && -+ p->nr_cpus_allowed > 1)) { -+ if (p->sched_class == &rt_sched_class) -+ task_rq(p)->rt.rt_nr_migratory += delta; -+ else -+ task_rq(p)->dl.dl_nr_migratory += delta; -+ } -+} -+ -+static inline void -+migrate_disable_update_cpus_allowed(struct task_struct *p) -+{ -+ struct rq *rq; -+ struct rq_flags rf; -+ -+ p->cpus_ptr = cpumask_of(smp_processor_id()); -+ -+ rq = task_rq_lock(p, &rf); -+ update_nr_migratory(p, -1); -+ p->nr_cpus_allowed = 1; -+ task_rq_unlock(rq, p, &rf); -+} -+ -+static inline void -+migrate_enable_update_cpus_allowed(struct task_struct *p) -+{ -+ struct rq *rq; -+ struct rq_flags rf; -+ -+ p->cpus_ptr = &p->cpus_mask; -+ -+ rq = task_rq_lock(p, &rf); -+ p->nr_cpus_allowed = cpumask_weight(&p->cpus_mask); -+ update_nr_migratory(p, 1); -+ task_rq_unlock(rq, p, &rf); -+} -+ - void migrate_disable(void) - { - struct task_struct *p = current; -@@ -7175,10 +7216,9 @@ void migrate_disable(void) - } - - preempt_disable(); -- p->migrate_disable = 1; - -- p->cpus_ptr = cpumask_of(smp_processor_id()); -- p->nr_cpus_allowed = 1; -+ migrate_disable_update_cpus_allowed(p); -+ p->migrate_disable = 1; - - preempt_enable(); - } -@@ -7210,9 +7250,8 @@ void migrate_enable(void) - - preempt_disable(); - -- p->cpus_ptr = &p->cpus_mask; -- p->nr_cpus_allowed = cpumask_weight(&p->cpus_mask); - p->migrate_disable = 0; -+ migrate_enable_update_cpus_allowed(p); - - if (p->migrate_disable_update) { - struct rq *rq; |