sched: replace PF_THREAD_BOUND with PF_NO_SETAFFINITY
PF_THREAD_BOUND was originally used to mark kernel threads which were bound to a specific CPU using kthread_bind() and a task with the flag set allows cpus_allowed modifications only to itself. Workqueue is currently abusing it to prevent userland from meddling with cpus_allowed of workqueue workers. What we need is a flag to prevent userland from messing with cpus_allowed of certain kernel tasks. In kernel, anyone can (incorrectly) squash the flag, and, for worker-type usages, restricting cpus_allowed modification to the task itself doesn't provide meaningful extra proection as other tasks can inject work items to the task anyway. This patch replaces PF_THREAD_BOUND with PF_NO_SETAFFINITY. sched_setaffinity() checks the flag and return -EINVAL if set. set_cpus_allowed_ptr() is no longer affected by the flag. This will allow simplifying workqueue worker CPU affinity management. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de>
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@@ -1793,7 +1793,7 @@ extern void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut,
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#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
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#define PF_SPREAD_PAGE 0x01000000 /* Spread page cache over cpuset */
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#define PF_SPREAD_SLAB 0x02000000 /* Spread some slab caches over cpuset */
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#define PF_THREAD_BOUND 0x04000000 /* Thread bound to specific cpu */
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#define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_allowed */
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#define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */
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#define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */
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#define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */
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