From ba15518c2610e777f141b55363b75f410eda7822 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 7 Sep 2017 11:13:38 +0200 Subject: sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs commit 50e76632339d4655859523a39249dd95ee5e93e7 upstream. Cpusets vs. suspend-resume is _completely_ broken. And it got noticed because it now resulted in non-cpuset usage breaking too. On suspend cpuset_cpu_inactive() doesn't call into cpuset_update_active_cpus() because it doesn't want to move tasks about, there is no need, all tasks are frozen and won't run again until after we've resumed everything. But this means that when we finally do call into cpuset_update_active_cpus() after resuming the last frozen cpu in cpuset_cpu_active(), the top_cpuset will not have any difference with the cpu_active_mask and this it will not in fact do _anything_. So the cpuset configuration will not be restored. This was largely hidden because we would unconditionally create identity domains and mobile users would not in fact use cpusets much. And servers what do use cpusets tend to not suspend-resume much. An addition problem is that we'd not in fact wait for the cpuset work to finish before resuming the tasks, allowing spurious migrations outside of the specified domains. Fix the rebuild by introducing cpuset_force_rebuild() and fix the ordering with cpuset_wait_for_hotplug(). Reported-by: Andy Lutomirski Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Rafael J. Wysocki Cc: Tejun Heo Cc: Thomas Gleixner Fixes: deb7aa308ea2 ("cpuset: reorganize CPU / memory hotplug handling") Link: http://lkml.kernel.org/r/20170907091338.orwxrqkbfkki3c24@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar Signed-off-by: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- kernel/cpuset.c | 16 +++++++++++++++- kernel/power/process.c | 5 ++++- kernel/sched/core.c | 7 +++---- 3 files changed, 22 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 03a3a6e94eb9..511b1dd8ff09 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -2276,6 +2276,13 @@ retry: mutex_unlock(&cpuset_mutex); } +static bool force_rebuild; + +void cpuset_force_rebuild(void) +{ + force_rebuild = true; +} + /** * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset * @@ -2350,8 +2357,10 @@ static void cpuset_hotplug_workfn(struct work_struct *work) } /* rebuild sched domains if cpus_allowed has changed */ - if (cpus_updated) + if (cpus_updated || force_rebuild) { + force_rebuild = false; rebuild_sched_domains(); + } } void cpuset_update_active_cpus(bool cpu_online) @@ -2370,6 +2379,11 @@ void cpuset_update_active_cpus(bool cpu_online) schedule_work(&cpuset_hotplug_work); } +void cpuset_wait_for_hotplug(void) +{ + flush_work(&cpuset_hotplug_work); +} + /* * Keep top_cpuset.mems_allowed tracking node_states[N_MEMORY]. * Call this routine anytime after node_states[N_MEMORY] changes. diff --git a/kernel/power/process.c b/kernel/power/process.c index 2fba066e125f..8ea24ded1dab 100644 --- a/kernel/power/process.c +++ b/kernel/power/process.c @@ -18,8 +18,9 @@ #include #include #include +#include -/* +/* * Timeout for stopping processes */ unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC; @@ -200,6 +201,8 @@ void thaw_processes(void) __usermodehelper_set_disable_depth(UMH_FREEZING); thaw_workqueues(); + cpuset_wait_for_hotplug(); + read_lock(&tasklist_lock); for_each_process_thread(g, p) { /* No other threads should have PF_SUSPEND_TASK set */ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2098954c690f..d7dda36fbc7b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7292,16 +7292,15 @@ static void cpuset_cpu_active(void) * operation in the resume sequence, just build a single sched * domain, ignoring cpusets. */ - num_cpus_frozen--; - if (likely(num_cpus_frozen)) { - partition_sched_domains(1, NULL, NULL); + partition_sched_domains(1, NULL, NULL); + if (--num_cpus_frozen) return; - } /* * This is the last CPU online operation. So fall through and * restore the original sched domains by considering the * cpuset configurations. */ + cpuset_force_rebuild(); } cpuset_update_active_cpus(true); } -- cgit v1.2.3