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>, Li Zefan <lizefan@huawei.com>, Johannes Weiner <hannes@cmpxchg.org>, Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>, Vincent Guittot <vincent.guittot@linaro.org>, kernel-team@android.com Subject: [PATCH v4 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity Date: Tue, 24 Nov 2020 15:50:32 +0000 [thread overview] Message-ID: <20201124155039.13804-8-will@kernel.org> (raw) In-Reply-To: <20201124155039.13804-1-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 userspace can carefully manage the affinity masks for such tasks, one place where it is particularly problematic is execve() because the CPU on which the execve() is occurring may be incompatible with the new application image. In such a situation, it is desirable to restrict the affinity mask of the task and ensure that the new image is entered on a compatible CPU. From userspace's point of view, this looks the same as if the incompatible CPUs have been hotplugged off in its affinity mask. In preparation for restricting the affinity mask for compat tasks on arm64 systems without uniform support for 32-bit applications, introduce a restrict_cpus_allowed_ptr(), which allows the current affinity mask for a task to be shrunk to the intersection of a parameter mask. Signed-off-by: Will Deacon <will@kernel.org> --- include/linux/sched.h | 1 + kernel/sched/core.c | 73 ++++++++++++++++++++++++++++++++++--------- 2 files changed, 59 insertions(+), 15 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 063cd120b459..1cd12c3ce9ee 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1631,6 +1631,7 @@ extern int task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_ #ifdef CONFIG_SMP extern void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask); extern int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask); +extern int restrict_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *mask); #else static inline void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) { diff --git a/kernel/sched/core.c b/kernel/sched/core.c index d2003a7d5ab5..818c8f7bdf2a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1860,24 +1860,18 @@ void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) } /* - * Change a given task's CPU affinity. Migrate the thread to a - * proper CPU and schedule it away if the CPU it's executing on - * is removed from the allowed bitmask. - * - * NOTE: the caller must have a valid reference to the task, the - * task must not exit() & deallocate itself prematurely. The - * call is not atomic; no spinlocks may be held. + * Called with both p->pi_lock and rq->lock held; drops both before returning. */ -static int __set_cpus_allowed_ptr(struct task_struct *p, - const struct cpumask *new_mask, bool check) +static int __set_cpus_allowed_ptr_locked(struct task_struct *p, + const struct cpumask *new_mask, + bool check, + struct rq *rq, + struct rq_flags *rf) { const struct cpumask *cpu_valid_mask = cpu_active_mask; unsigned int dest_cpu; - struct rq_flags rf; - struct rq *rq; int ret = 0; - rq = task_rq_lock(p, &rf); update_rq_clock(rq); if (p->flags & PF_KTHREAD) { @@ -1929,7 +1923,7 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, if (task_running(rq, p) || p->state == TASK_WAKING) { struct migration_arg arg = { p, dest_cpu }; /* Need help from migration thread: drop lock and wait. */ - task_rq_unlock(rq, p, &rf); + task_rq_unlock(rq, p, rf); stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg); return 0; } else if (task_on_rq_queued(p)) { @@ -1937,20 +1931,69 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, * OK, since we're going to drop the lock immediately * afterwards anyway. */ - rq = move_queued_task(rq, &rf, p, dest_cpu); + rq = move_queued_task(rq, rf, p, dest_cpu); } out: - task_rq_unlock(rq, p, &rf); + task_rq_unlock(rq, p, rf); return ret; } +/* + * Change a given task's CPU affinity. Migrate the thread to a + * proper CPU and schedule it away if the CPU it's executing on + * is removed from the allowed bitmask. + * + * NOTE: the caller must have a valid reference to the task, the + * task must not exit() & deallocate itself prematurely. The + * call is not atomic; no spinlocks may be held. + */ +static int __set_cpus_allowed_ptr(struct task_struct *p, + const struct cpumask *new_mask, bool check) +{ + struct rq_flags rf; + struct rq *rq; + + rq = task_rq_lock(p, &rf); + return __set_cpus_allowed_ptr_locked(p, new_mask, check, rq, &rf); +} + int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) { return __set_cpus_allowed_ptr(p, new_mask, false); } EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); +/* + * Change a given task's CPU affinity to the intersection of its current + * affinity mask and @subset_mask. If the resulting mask is empty, leave + * the affinity unchanged and return -EINVAL. + */ +int restrict_cpus_allowed_ptr(struct task_struct *p, + const struct cpumask *subset_mask) +{ + struct rq_flags rf; + struct rq *rq; + cpumask_var_t new_mask; + int retval; + + if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) + return -ENOMEM; + + rq = task_rq_lock(p, &rf); + if (!cpumask_and(new_mask, &p->cpus_mask, subset_mask)) { + task_rq_unlock(rq, p, &rf); + retval = -EINVAL; + goto out_free_new_mask; + } + + retval = __set_cpus_allowed_ptr_locked(p, new_mask, false, rq, &rf); + +out_free_new_mask: + free_cpumask_var(new_mask); + return retval; +} + void set_task_cpu(struct task_struct *p, unsigned int new_cpu) { #ifdef CONFIG_SCHED_DEBUG -- 2.29.2.454.gaff20da3a2-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, Marc Zyngier <maz@kernel.org>, kernel-team@android.com, Vincent Guittot <vincent.guittot@linaro.org>, Juri Lelli <juri.lelli@redhat.com>, Quentin Perret <qperret@google.com>, Peter Zijlstra <peterz@infradead.org>, Catalin Marinas <catalin.marinas@arm.com>, Johannes Weiner <hannes@cmpxchg.org>, linux-kernel@vger.kernel.org, Qais Yousef <qais.yousef@arm.com>, Suren Baghdasaryan <surenb@google.com>, Ingo Molnar <mingo@redhat.com>, Li Zefan <lizefan@huawei.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Tejun Heo <tj@kernel.org>, Will Deacon <will@kernel.org>, Morten Rasmussen <morten.rasmussen@arm.com> Subject: [PATCH v4 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity Date: Tue, 24 Nov 2020 15:50:32 +0000 [thread overview] Message-ID: <20201124155039.13804-8-will@kernel.org> (raw) In-Reply-To: <20201124155039.13804-1-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 userspace can carefully manage the affinity masks for such tasks, one place where it is particularly problematic is execve() because the CPU on which the execve() is occurring may be incompatible with the new application image. In such a situation, it is desirable to restrict the affinity mask of the task and ensure that the new image is entered on a compatible CPU. From userspace's point of view, this looks the same as if the incompatible CPUs have been hotplugged off in its affinity mask. In preparation for restricting the affinity mask for compat tasks on arm64 systems without uniform support for 32-bit applications, introduce a restrict_cpus_allowed_ptr(), which allows the current affinity mask for a task to be shrunk to the intersection of a parameter mask. Signed-off-by: Will Deacon <will@kernel.org> --- include/linux/sched.h | 1 + kernel/sched/core.c | 73 ++++++++++++++++++++++++++++++++++--------- 2 files changed, 59 insertions(+), 15 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 063cd120b459..1cd12c3ce9ee 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1631,6 +1631,7 @@ extern int task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_ #ifdef CONFIG_SMP extern void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask); extern int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask); +extern int restrict_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *mask); #else static inline void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) { diff --git a/kernel/sched/core.c b/kernel/sched/core.c index d2003a7d5ab5..818c8f7bdf2a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1860,24 +1860,18 @@ void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) } /* - * Change a given task's CPU affinity. Migrate the thread to a - * proper CPU and schedule it away if the CPU it's executing on - * is removed from the allowed bitmask. - * - * NOTE: the caller must have a valid reference to the task, the - * task must not exit() & deallocate itself prematurely. The - * call is not atomic; no spinlocks may be held. + * Called with both p->pi_lock and rq->lock held; drops both before returning. */ -static int __set_cpus_allowed_ptr(struct task_struct *p, - const struct cpumask *new_mask, bool check) +static int __set_cpus_allowed_ptr_locked(struct task_struct *p, + const struct cpumask *new_mask, + bool check, + struct rq *rq, + struct rq_flags *rf) { const struct cpumask *cpu_valid_mask = cpu_active_mask; unsigned int dest_cpu; - struct rq_flags rf; - struct rq *rq; int ret = 0; - rq = task_rq_lock(p, &rf); update_rq_clock(rq); if (p->flags & PF_KTHREAD) { @@ -1929,7 +1923,7 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, if (task_running(rq, p) || p->state == TASK_WAKING) { struct migration_arg arg = { p, dest_cpu }; /* Need help from migration thread: drop lock and wait. */ - task_rq_unlock(rq, p, &rf); + task_rq_unlock(rq, p, rf); stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg); return 0; } else if (task_on_rq_queued(p)) { @@ -1937,20 +1931,69 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, * OK, since we're going to drop the lock immediately * afterwards anyway. */ - rq = move_queued_task(rq, &rf, p, dest_cpu); + rq = move_queued_task(rq, rf, p, dest_cpu); } out: - task_rq_unlock(rq, p, &rf); + task_rq_unlock(rq, p, rf); return ret; } +/* + * Change a given task's CPU affinity. Migrate the thread to a + * proper CPU and schedule it away if the CPU it's executing on + * is removed from the allowed bitmask. + * + * NOTE: the caller must have a valid reference to the task, the + * task must not exit() & deallocate itself prematurely. The + * call is not atomic; no spinlocks may be held. + */ +static int __set_cpus_allowed_ptr(struct task_struct *p, + const struct cpumask *new_mask, bool check) +{ + struct rq_flags rf; + struct rq *rq; + + rq = task_rq_lock(p, &rf); + return __set_cpus_allowed_ptr_locked(p, new_mask, check, rq, &rf); +} + int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) { return __set_cpus_allowed_ptr(p, new_mask, false); } EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); +/* + * Change a given task's CPU affinity to the intersection of its current + * affinity mask and @subset_mask. If the resulting mask is empty, leave + * the affinity unchanged and return -EINVAL. + */ +int restrict_cpus_allowed_ptr(struct task_struct *p, + const struct cpumask *subset_mask) +{ + struct rq_flags rf; + struct rq *rq; + cpumask_var_t new_mask; + int retval; + + if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) + return -ENOMEM; + + rq = task_rq_lock(p, &rf); + if (!cpumask_and(new_mask, &p->cpus_mask, subset_mask)) { + task_rq_unlock(rq, p, &rf); + retval = -EINVAL; + goto out_free_new_mask; + } + + retval = __set_cpus_allowed_ptr_locked(p, new_mask, false, rq, &rf); + +out_free_new_mask: + free_cpumask_var(new_mask); + return retval; +} + void set_task_cpu(struct task_struct *p, unsigned int new_cpu) { #ifdef CONFIG_SCHED_DEBUG -- 2.29.2.454.gaff20da3a2-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:[~2020-11-24 15:51 UTC|newest] Thread overview: 122+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-11-24 15:50 [PATCH v4 00/14] An alternative series for asymmetric AArch32 systems Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-24 15:50 ` [PATCH v4 01/14] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-24 15:50 ` [PATCH v4 02/14] arm64: Allow mismatched 32-bit EL0 support Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 10:25 ` Marc Zyngier 2020-11-27 10:25 ` Marc Zyngier 2020-11-27 11:50 ` Will Deacon 2020-11-27 11:50 ` Will Deacon 2020-11-27 13:09 ` Qais Yousef 2020-11-27 13:09 ` Qais Yousef 2020-12-01 16:56 ` Will Deacon 2020-12-01 16:56 ` Will Deacon 2020-12-02 13:16 ` Qais Yousef 2020-12-02 13:16 ` Qais Yousef 2020-11-24 15:50 ` [PATCH v4 03/14] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 10:26 ` Marc Zyngier 2020-11-27 10:26 ` Marc Zyngier 2020-11-27 11:53 ` Will Deacon 2020-11-27 11:53 ` Will Deacon 2020-11-27 17:14 ` Marc Zyngier 2020-11-27 17:14 ` Marc Zyngier 2020-11-27 17:24 ` Quentin Perret 2020-11-27 17:24 ` Quentin Perret 2020-11-27 18:16 ` Marc Zyngier 2020-11-27 18:16 ` Marc Zyngier 2020-12-01 16:57 ` Will Deacon 2020-12-01 16:57 ` Will Deacon 2020-12-02 8:18 ` Marc Zyngier 2020-12-02 8:18 ` Marc Zyngier 2020-12-02 17:27 ` Will Deacon 2020-12-02 17:27 ` Will Deacon 2020-11-24 15:50 ` [PATCH v4 04/14] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 13:12 ` Qais Yousef 2020-11-27 13:12 ` Qais Yousef 2020-12-01 16:56 ` Will Deacon 2020-12-01 16:56 ` Will Deacon 2020-12-02 13:52 ` Qais Yousef 2020-12-02 13:52 ` Qais Yousef 2020-12-02 17:42 ` Will Deacon 2020-12-02 17:42 ` Will Deacon 2020-11-24 15:50 ` [PATCH v4 05/14] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-24 15:50 ` [PATCH v4 06/14] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 13:17 ` Qais Yousef 2020-11-27 13:17 ` Qais Yousef 2020-12-01 16:56 ` Will Deacon 2020-12-01 16:56 ` Will Deacon 2020-11-24 15:50 ` Will Deacon [this message] 2020-11-24 15:50 ` [PATCH v4 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity Will Deacon 2020-11-27 9:49 ` Quentin Perret 2020-11-27 9:49 ` Quentin Perret 2020-11-27 13:19 ` Qais Yousef 2020-11-27 13:19 ` Qais Yousef 2020-12-01 16:56 ` Will Deacon 2020-12-01 16:56 ` Will Deacon 2020-12-02 13:06 ` Qais Yousef 2020-12-02 13:06 ` Qais Yousef 2020-11-24 15:50 ` [PATCH v4 08/14] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 10:01 ` Quentin Perret 2020-11-27 10:01 ` Quentin Perret 2020-11-27 13:23 ` Qais Yousef 2020-11-27 13:23 ` Qais Yousef 2020-12-01 16:55 ` Will Deacon 2020-12-01 16:55 ` Will Deacon 2020-12-02 14:07 ` Qais Yousef 2020-12-02 14:07 ` Qais Yousef 2020-11-24 15:50 ` [PATCH v4 09/14] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 13:32 ` Qais Yousef 2020-11-27 13:32 ` Qais Yousef 2020-11-30 17:05 ` Qais Yousef 2020-11-30 17:05 ` Qais Yousef 2020-11-30 17:36 ` Quentin Perret 2020-11-30 17:36 ` Quentin Perret 2020-12-01 11:58 ` Qais Yousef 2020-12-01 11:58 ` Qais Yousef 2020-12-01 12:37 ` Quentin Perret 2020-12-01 12:37 ` Quentin Perret 2020-12-01 14:11 ` Qais Yousef 2020-12-01 14:11 ` Qais Yousef 2020-12-01 15:56 ` Quentin Perret 2020-12-01 15:56 ` Quentin Perret 2020-12-01 22:30 ` Will Deacon 2020-12-01 22:30 ` Will Deacon 2020-12-02 11:34 ` Qais Yousef 2020-12-02 11:34 ` Qais Yousef 2020-12-02 11:33 ` Qais Yousef 2020-12-02 11:33 ` Qais Yousef 2020-11-24 15:50 ` [PATCH v4 10/14] sched: Introduce arch_task_cpu_possible_mask() to limit fallback rq selection Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-24 15:50 ` [PATCH v4 11/14] sched: Reject CPU affinity changes based on arch_task_cpu_possible_mask() Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 9:54 ` Quentin Perret 2020-11-27 9:54 ` Quentin Perret 2020-11-24 15:50 ` [PATCH v4 12/14] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 13:41 ` Qais Yousef 2020-11-27 13:41 ` Qais Yousef 2020-12-01 22:13 ` Will Deacon 2020-12-01 22:13 ` Will Deacon 2020-12-02 12:59 ` Qais Yousef 2020-12-02 12:59 ` Qais Yousef 2020-12-02 17:42 ` Will Deacon 2020-12-02 17:42 ` Will Deacon 2020-12-02 18:08 ` Qais Yousef 2020-12-02 18:08 ` Qais Yousef 2020-11-24 15:50 ` [PATCH v4 13/14] arm64: Implement arch_task_cpu_possible_mask() Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 13:41 ` Qais Yousef 2020-11-27 13:41 ` Qais Yousef 2020-11-24 15:50 ` [PATCH v4 14/14] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon 2020-11-24 15:50 ` Will Deacon 2020-11-27 13:58 ` [PATCH v4 00/14] An alternative series for asymmetric AArch32 systems Qais Yousef 2020-11-27 13:58 ` Qais Yousef 2020-12-05 20:43 ` Pavel Machek 2020-12-05 20:43 ` Pavel Machek
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