From: Will Deacon <will@kernel.org> To: linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>, Catalin Marinas <catalin.marinas@arm.com>, Marc Zyngier <maz@kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Peter Zijlstra <peterz@infradead.org>, Morten Rasmussen <morten.rasmussen@arm.com>, Qais Yousef <qais.yousef@arm.com>, Suren Baghdasaryan <surenb@google.com>, Quentin Perret <qperret@google.com>, Tejun Heo <tj@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>, Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>, Vincent Guittot <vincent.guittot@linaro.org>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Daniel Bristot de Oliveira <bristot@redhat.com>, kernel-team@android.com Subject: [PATCH v7 16/22] sched: Defer wakeup in ttwu() for unschedulable frozen tasks Date: Tue, 25 May 2021 16:14:26 +0100 [thread overview] Message-ID: <20210525151432.16875-17-will@kernel.org> (raw) In-Reply-To: <20210525151432.16875-1-will@kernel.org> Asymmetric systems may not offer the same level of userspace ISA support across all CPUs, meaning that some applications cannot be executed by some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do not feature support for 32-bit applications on both clusters. Although we take care to prevent explicit hot-unplug of all 32-bit capable CPUs on such a system, this is required when suspending on some SoCs where the firmware mandates that the suspend/resume operation is handled by CPU 0, which may not be capable of running 32-bit tasks. Consequently, there is a window on the resume path where no 32-bit capable CPUs are available for scheduling and waking up a 32-bit task will result in a scheduler BUG() due to failure of select_fallback_rq(): | kernel BUG at kernel/sched/core.c:2858! | Internal error: Oops - BUG: 0 [#1] PREEMPT SMP | ... | Call trace: | select_fallback_rq+0x4b0/0x4e4 | try_to_wake_up.llvm.4388853297126348405+0x460/0x5b0 | default_wake_function+0x1c/0x30 | autoremove_wake_function+0x1c/0x60 | __wake_up_common.llvm.11763074518265335900+0x100/0x1b8 | __wake_up+0x78/0xc4 | ep_poll_callback+0x20c/0x3fc Prevent wakeups of unschedulable frozen tasks in ttwu() and instead defer the wakeup to __thaw_tasks(), which runs only once all the secondary CPUs are back online. Signed-off-by: Will Deacon <will@kernel.org> --- kernel/freezer.c | 10 +++++++++- kernel/sched/core.c | 13 +++++++++++++ 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/kernel/freezer.c b/kernel/freezer.c index dc520f01f99d..8f3d950c2a87 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -11,6 +11,7 @@ #include <linux/syscalls.h> #include <linux/freezer.h> #include <linux/kthread.h> +#include <linux/mmu_context.h> /* total number of freezing conditions in effect */ atomic_t system_freezing_cnt = ATOMIC_INIT(0); @@ -146,9 +147,16 @@ bool freeze_task(struct task_struct *p) void __thaw_task(struct task_struct *p) { unsigned long flags; + const struct cpumask *mask = task_cpu_possible_mask(p); spin_lock_irqsave(&freezer_lock, flags); - if (frozen(p)) + /* + * Wake up frozen tasks. On asymmetric systems where tasks cannot + * run on all CPUs, ttwu() may have deferred a wakeup generated + * before thaw_secondary_cpus() had completed so we generate + * additional wakeups here for tasks in the PF_FREEZER_SKIP state. + */ + if (frozen(p) || (frozen_or_skipped(p) && mask != cpu_possible_mask)) wake_up_process(p); spin_unlock_irqrestore(&freezer_lock, flags); } diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 42e2aecf087c..6cb9677d635a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3529,6 +3529,19 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) if (!(p->state & state)) goto unlock; +#ifdef CONFIG_FREEZER + /* + * If we're going to wake up a thread which may be frozen, then + * we can only do so if we have an active CPU which is capable of + * running it. This may not be the case when resuming from suspend, + * as the secondary CPUs may not yet be back online. See __thaw_task() + * for the actual wakeup. + */ + if (unlikely(frozen_or_skipped(p)) && + !cpumask_intersects(cpu_active_mask, task_cpu_possible_mask(p))) + goto unlock; +#endif + trace_sched_waking(p); /* We're going to change ->state: */ -- 2.31.1.818.g46aad6cb9e-goog
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org> To: linux-arm-kernel@lists.infradead.org Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>, Catalin Marinas <catalin.marinas@arm.com>, Marc Zyngier <maz@kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Peter Zijlstra <peterz@infradead.org>, Morten Rasmussen <morten.rasmussen@arm.com>, Qais Yousef <qais.yousef@arm.com>, Suren Baghdasaryan <surenb@google.com>, Quentin Perret <qperret@google.com>, Tejun Heo <tj@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>, Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>, Vincent Guittot <vincent.guittot@linaro.org>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Daniel Bristot de Oliveira <bristot@redhat.com>, kernel-team@android.com Subject: [PATCH v7 16/22] sched: Defer wakeup in ttwu() for unschedulable frozen tasks Date: Tue, 25 May 2021 16:14:26 +0100 [thread overview] Message-ID: <20210525151432.16875-17-will@kernel.org> (raw) In-Reply-To: <20210525151432.16875-1-will@kernel.org> Asymmetric systems may not offer the same level of userspace ISA support across all CPUs, meaning that some applications cannot be executed by some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do not feature support for 32-bit applications on both clusters. Although we take care to prevent explicit hot-unplug of all 32-bit capable CPUs on such a system, this is required when suspending on some SoCs where the firmware mandates that the suspend/resume operation is handled by CPU 0, which may not be capable of running 32-bit tasks. Consequently, there is a window on the resume path where no 32-bit capable CPUs are available for scheduling and waking up a 32-bit task will result in a scheduler BUG() due to failure of select_fallback_rq(): | kernel BUG at kernel/sched/core.c:2858! | Internal error: Oops - BUG: 0 [#1] PREEMPT SMP | ... | Call trace: | select_fallback_rq+0x4b0/0x4e4 | try_to_wake_up.llvm.4388853297126348405+0x460/0x5b0 | default_wake_function+0x1c/0x30 | autoremove_wake_function+0x1c/0x60 | __wake_up_common.llvm.11763074518265335900+0x100/0x1b8 | __wake_up+0x78/0xc4 | ep_poll_callback+0x20c/0x3fc Prevent wakeups of unschedulable frozen tasks in ttwu() and instead defer the wakeup to __thaw_tasks(), which runs only once all the secondary CPUs are back online. Signed-off-by: Will Deacon <will@kernel.org> --- kernel/freezer.c | 10 +++++++++- kernel/sched/core.c | 13 +++++++++++++ 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/kernel/freezer.c b/kernel/freezer.c index dc520f01f99d..8f3d950c2a87 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -11,6 +11,7 @@ #include <linux/syscalls.h> #include <linux/freezer.h> #include <linux/kthread.h> +#include <linux/mmu_context.h> /* total number of freezing conditions in effect */ atomic_t system_freezing_cnt = ATOMIC_INIT(0); @@ -146,9 +147,16 @@ bool freeze_task(struct task_struct *p) void __thaw_task(struct task_struct *p) { unsigned long flags; + const struct cpumask *mask = task_cpu_possible_mask(p); spin_lock_irqsave(&freezer_lock, flags); - if (frozen(p)) + /* + * Wake up frozen tasks. On asymmetric systems where tasks cannot + * run on all CPUs, ttwu() may have deferred a wakeup generated + * before thaw_secondary_cpus() had completed so we generate + * additional wakeups here for tasks in the PF_FREEZER_SKIP state. + */ + if (frozen(p) || (frozen_or_skipped(p) && mask != cpu_possible_mask)) wake_up_process(p); spin_unlock_irqrestore(&freezer_lock, flags); } diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 42e2aecf087c..6cb9677d635a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3529,6 +3529,19 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) if (!(p->state & state)) goto unlock; +#ifdef CONFIG_FREEZER + /* + * If we're going to wake up a thread which may be frozen, then + * we can only do so if we have an active CPU which is capable of + * running it. This may not be the case when resuming from suspend, + * as the secondary CPUs may not yet be back online. See __thaw_task() + * for the actual wakeup. + */ + if (unlikely(frozen_or_skipped(p)) && + !cpumask_intersects(cpu_active_mask, task_cpu_possible_mask(p))) + goto unlock; +#endif + trace_sched_waking(p); /* We're going to change ->state: */ -- 2.31.1.818.g46aad6cb9e-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-05-25 15:16 UTC|newest] Thread overview: 114+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-25 15:14 [PATCH v7 00/22] Add support for 32-bit tasks on asymmetric AArch32 systems Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 01/22] sched: Favour predetermined active CPU as migration destination Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-26 11:14 ` Valentin Schneider 2021-05-26 11:14 ` Valentin Schneider 2021-05-26 12:32 ` Peter Zijlstra 2021-05-26 12:32 ` Peter Zijlstra 2021-05-26 12:36 ` Valentin Schneider 2021-05-26 12:36 ` Valentin Schneider 2021-05-26 16:03 ` Will Deacon 2021-05-26 16:03 ` Will Deacon 2021-05-26 17:46 ` Valentin Schneider 2021-05-26 17:46 ` Valentin Schneider 2021-05-25 15:14 ` [PATCH v7 02/22] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 03/22] arm64: Allow mismatched 32-bit EL0 support Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 04/22] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 05/22] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 06/22] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 07/22] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 08/22] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-26 15:02 ` Peter Zijlstra 2021-05-26 15:02 ` Peter Zijlstra 2021-05-26 16:07 ` Will Deacon 2021-05-26 16:07 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 09/22] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 10/22] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-26 15:15 ` Peter Zijlstra 2021-05-26 15:15 ` Peter Zijlstra 2021-05-26 16:12 ` Will Deacon 2021-05-26 16:12 ` Will Deacon 2021-05-26 17:56 ` Peter Zijlstra 2021-05-26 17:56 ` Peter Zijlstra 2021-05-26 18:59 ` Will Deacon 2021-05-26 18:59 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 11/22] sched: Introduce task_struct::user_cpus_ptr to track requested affinity Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 12/22] sched: Split the guts of sched_setaffinity() into a helper function Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 13/22] sched: Allow task CPU affinity to be restricted on asymmetric systems Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-26 16:20 ` Peter Zijlstra 2021-05-26 16:20 ` Peter Zijlstra 2021-05-26 16:35 ` Will Deacon 2021-05-26 16:35 ` Will Deacon 2021-05-26 16:30 ` Peter Zijlstra 2021-05-26 16:30 ` Peter Zijlstra 2021-05-26 17:02 ` Will Deacon 2021-05-26 17:02 ` Will Deacon 2021-05-27 7:56 ` Peter Zijlstra 2021-05-27 7:56 ` Peter Zijlstra 2021-05-25 15:14 ` [PATCH v7 14/22] sched: Introduce task_cpus_dl_admissible() to check proposed affinity Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 15/22] freezer: Add frozen_or_skipped() helper function Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` Will Deacon [this message] 2021-05-25 15:14 ` [PATCH v7 16/22] sched: Defer wakeup in ttwu() for unschedulable frozen tasks Will Deacon 2021-05-27 14:10 ` Peter Zijlstra 2021-05-27 14:10 ` Peter Zijlstra 2021-05-27 14:31 ` Peter Zijlstra 2021-05-27 14:31 ` Peter Zijlstra 2021-05-27 14:44 ` Will Deacon 2021-05-27 14:44 ` Will Deacon 2021-05-27 14:55 ` Peter Zijlstra 2021-05-27 14:55 ` Peter Zijlstra 2021-05-27 14:50 ` Peter Zijlstra 2021-05-27 14:50 ` Peter Zijlstra 2021-05-28 10:49 ` Peter Zijlstra 2021-05-28 10:49 ` Peter Zijlstra 2021-05-27 14:36 ` Will Deacon 2021-05-27 14:36 ` Will Deacon 2021-06-01 8:21 ` [RFC][PATCH] freezer,sched: Rewrite core freezer logic Peter Zijlstra 2021-06-01 8:21 ` Peter Zijlstra 2021-06-01 11:27 ` Peter Zijlstra 2021-06-01 11:27 ` Peter Zijlstra 2021-06-02 12:54 ` Will Deacon 2021-06-02 12:54 ` Will Deacon 2021-06-03 10:35 ` Peter Zijlstra 2021-06-03 10:35 ` Peter Zijlstra 2021-06-03 10:58 ` Will Deacon 2021-06-03 10:58 ` Will Deacon 2021-06-03 11:26 ` Peter Zijlstra 2021-06-03 11:26 ` Peter Zijlstra 2021-06-03 11:36 ` Will Deacon 2021-06-03 11:36 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 17/22] arm64: Implement task_cpu_possible_mask() Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 18/22] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 19/22] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 20/22] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 21/22] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 15:14 ` [PATCH v7 22/22] Documentation: arm64: describe asymmetric 32-bit support Will Deacon 2021-05-25 15:14 ` Will Deacon 2021-05-25 17:13 ` Marc Zyngier 2021-05-25 17:13 ` Marc Zyngier 2021-05-25 17:27 ` Will Deacon 2021-05-25 17:27 ` Will Deacon 2021-05-25 18:11 ` Marc Zyngier 2021-05-25 18:11 ` Marc Zyngier 2021-05-26 16:00 ` Will Deacon 2021-05-26 16:00 ` Will Deacon
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