From 717a94b5fc7092afebe9c93791f29b2d8e5d297a Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Fri, 7 Apr 2017 10:03:26 +1000 Subject: sched/core: Remove 'task' parameter and rename tsk_restore_flags() to current_restore_flags() It is not safe for one thread to modify the ->flags of another thread as there is no locking that can protect the update. So tsk_restore_flags(), which takes a task pointer and modifies the flags, is an invitation to do the wrong thing. All current users pass "current" as the task, so no developers have accepted that invitation. It would be best to ensure it remains that way. So rename tsk_restore_flags() to current_restore_flags() and don't pass in a task_struct pointer. Always operate on current->flags. Signed-off-by: NeilBrown Cc: Linus Torvalds Cc: Mel Gorman Cc: Michal Hocko Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- include/linux/sched.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index d67eee84fd43..0978fb74e45a 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1286,10 +1286,10 @@ TASK_PFA_TEST(LMK_WAITING, lmk_waiting) TASK_PFA_SET(LMK_WAITING, lmk_waiting) static inline void -tsk_restore_flags(struct task_struct *task, unsigned long orig_flags, unsigned long flags) +current_restore_flags(unsigned long orig_flags, unsigned long flags) { - task->flags &= ~flags; - task->flags |= orig_flags & flags; + current->flags &= ~flags; + current->flags |= orig_flags & flags; } extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial); -- cgit v1.2.3 From 0e8d6a9336b487a1dd6f1991ff376e669d4c87c6 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 12 Apr 2017 22:07:28 +0200 Subject: workqueue: Provide work_on_cpu_safe() work_on_cpu() is not protected against CPU hotplug. For code which requires to be either executed on an online CPU or to fail if the CPU is not available the callsite would have to protect against CPU hotplug. Provide a function which does get/put_online_cpus() around the call to work_on_cpu() and fails the call with -ENODEV if the target CPU is not online. Preparatory patch to convert several racy task affinity manipulations. Signed-off-by: Thomas Gleixner Acked-by: Tejun Heo Cc: Fenghua Yu Cc: Tony Luck Cc: Herbert Xu Cc: "Rafael J. Wysocki" Cc: Peter Zijlstra Cc: Benjamin Herrenschmidt Cc: Sebastian Siewior Cc: Lai Jiangshan Cc: Viresh Kumar Cc: Michael Ellerman Cc: "David S. Miller" Cc: Len Brown Link: http://lkml.kernel.org/r/20170412201042.262610721@linutronix.de Signed-off-by: Thomas Gleixner --- include/linux/workqueue.h | 5 +++++ kernel/workqueue.c | 23 +++++++++++++++++++++++ 2 files changed, 28 insertions(+) (limited to 'include/linux') diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index bde063cefd04..c102ef65cb64 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -608,8 +608,13 @@ static inline long work_on_cpu(int cpu, long (*fn)(void *), void *arg) { return fn(arg); } +static inline long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg) +{ + return fn(arg); +} #else long work_on_cpu(int cpu, long (*fn)(void *), void *arg); +long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg); #endif /* CONFIG_SMP */ #ifdef CONFIG_FREEZER diff --git a/kernel/workqueue.c b/kernel/workqueue.c index c0168b7da1ea..5bf1be018628 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -4735,6 +4735,29 @@ long work_on_cpu(int cpu, long (*fn)(void *), void *arg) return wfc.ret; } EXPORT_SYMBOL_GPL(work_on_cpu); + +/** + * work_on_cpu_safe - run a function in thread context on a particular cpu + * @cpu: the cpu to run on + * @fn: the function to run + * @arg: the function argument + * + * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold + * any locks which would prevent @fn from completing. + * + * Return: The value @fn returns. + */ +long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg) +{ + long ret = -ENODEV; + + get_online_cpus(); + if (cpu_online(cpu)) + ret = work_on_cpu(cpu, fn, arg); + put_online_cpus(); + return ret; +} +EXPORT_SYMBOL_GPL(work_on_cpu_safe); #endif /* CONFIG_SMP */ #ifdef CONFIG_FREEZER -- cgit v1.2.3