From 34f971f6f7988be4d014eec3e3526bee6d007ffa Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 22 Sep 2010 13:53:15 +0200 Subject: sched: Create special class for stop/migrate work In order to separate the stop/migrate work thread from the SCHED_FIFO implementation, create a special class for it that is of higher priority than SCHED_FIFO itself. This currently solves a problem where cpu-hotplug consumes so much cpu-time that the SCHED_FIFO class gets throttled, but has the bandwidth replenishment timer pending on the now dead cpu. It is also required for when we add the planned deadline scheduling class above SCHED_FIFO, as the stop/migrate thread still needs to transcent those tasks. Tested-by: Heiko Carstens Signed-off-by: Peter Zijlstra LKML-Reference: <1285165776.2275.1022.camel@laptop> Signed-off-by: Ingo Molnar --- kernel/stop_machine.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'kernel/stop_machine.c') diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 4372ccb2512..090c28812ce 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -287,11 +287,12 @@ repeat: goto repeat; } +extern void sched_set_stop_task(int cpu, struct task_struct *stop); + /* manage stopper for a cpu, mostly lifted from sched migration thread mgmt */ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { - struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 }; unsigned int cpu = (unsigned long)hcpu; struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); struct task_struct *p; @@ -304,13 +305,13 @@ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, cpu); if (IS_ERR(p)) return NOTIFY_BAD; - sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m); get_task_struct(p); + kthread_bind(p, cpu); + sched_set_stop_task(cpu, p); stopper->thread = p; break; case CPU_ONLINE: - kthread_bind(stopper->thread, cpu); /* strictly unnecessary, as first user will wake it */ wake_up_process(stopper->thread); /* mark enabled */ @@ -325,6 +326,7 @@ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, { struct cpu_stop_work *work; + sched_set_stop_task(cpu, NULL); /* kill the stopper */ kthread_stop(stopper->thread); /* drain remaining works */ -- cgit v1.2.3-70-g09d2 From ca51c5a76345b28c6f1b742f9f5f0a6fc9afd9ca Mon Sep 17 00:00:00 2001 From: Rakib Mullick Date: Tue, 26 Oct 2010 14:22:44 -0700 Subject: kernel/stop_machine.c: fix unused variable warning kernel/stop_machine.c: In function `cpu_stopper_thread': kernel/stop_machine.c:265: warning: unused variable `ksym_buf' ksym_buf[] is unused if WARN_ON() is a no-op. Signed-off-by: Rakib Mullick Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/stop_machine.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/stop_machine.c') diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 090c28812ce..3cb4a9a8ae1 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -262,7 +262,7 @@ repeat: cpu_stop_fn_t fn = work->fn; void *arg = work->arg; struct cpu_stop_done *done = work->done; - char ksym_buf[KSYM_NAME_LEN]; + char ksym_buf[KSYM_NAME_LEN] __maybe_unused; __set_current_state(TASK_RUNNING); -- cgit v1.2.3-70-g09d2 From 4ce6494dbd8909718840bb88d5a699ef6ce5c212 Mon Sep 17 00:00:00 2001 From: Akinobu Mita Date: Tue, 26 Oct 2010 14:22:45 -0700 Subject: stop_machine: convert cpu notifier to return encapsulate errno value In commit e6bde73b07edeb703d4c89c1daabc09c303de11f ("cpu-hotplug: return better errno on cpu hotplug failure"), the cpu notifier can return an encapsulated errno value. This converts the cpu notifier to return an encapsulated errno value for stop_machine(). Signed-off-by: Akinobu Mita Cc: Rusty Russell Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/stop_machine.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'kernel/stop_machine.c') diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 3cb4a9a8ae1..2df820b03be 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -304,7 +304,7 @@ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, p = kthread_create(cpu_stopper_thread, stopper, "migration/%d", cpu); if (IS_ERR(p)) - return NOTIFY_BAD; + return notifier_from_errno(PTR_ERR(p)); get_task_struct(p); kthread_bind(p, cpu); sched_set_stop_task(cpu, p); @@ -372,7 +372,7 @@ static int __init cpu_stop_init(void) /* start one for the boot cpu */ err = cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_UP_PREPARE, bcpu); - BUG_ON(err == NOTIFY_BAD); + BUG_ON(err != NOTIFY_OK); cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu); register_cpu_notifier(&cpu_stop_cpu_notifier); -- cgit v1.2.3-70-g09d2