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Merge branch 'for-4.12-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup fixes from Tejun Heo: "Two cgroup fixes. One to address RCU delay of cpuset removal affecting userland visible behaviors. The other fixes a race condition between controller disable and cgroup removal" * 'for-4.12-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cpuset: consider dying css as offline cgroup: Prevent kill_css() from being called more than once
This commit is contained in:
commit
ba7b2387ad
4 changed files with 28 additions and 2 deletions
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@ -48,6 +48,7 @@ enum {
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CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
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CSS_RELEASED = (1 << 2), /* refcnt reached zero, released */
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CSS_VISIBLE = (1 << 3), /* css is visible to userland */
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CSS_DYING = (1 << 4), /* css is dying */
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};
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/* bits in struct cgroup flags field */
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@ -343,6 +343,26 @@ static inline bool css_tryget_online(struct cgroup_subsys_state *css)
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return true;
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}
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/**
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* css_is_dying - test whether the specified css is dying
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* @css: target css
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*
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* Test whether @css is in the process of offlining or already offline. In
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* most cases, ->css_online() and ->css_offline() callbacks should be
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* enough; however, the actual offline operations are RCU delayed and this
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* test returns %true also when @css is scheduled to be offlined.
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*
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* This is useful, for example, when the use case requires synchronous
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* behavior with respect to cgroup removal. cgroup removal schedules css
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* offlining but the css can seem alive while the operation is being
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* delayed. If the delay affects user visible semantics, this test can be
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* used to resolve the situation.
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*/
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static inline bool css_is_dying(struct cgroup_subsys_state *css)
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{
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return !(css->flags & CSS_NO_REF) && percpu_ref_is_dying(&css->refcnt);
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}
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/**
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* css_put - put a css reference
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* @css: target css
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@ -4265,6 +4265,11 @@ static void kill_css(struct cgroup_subsys_state *css)
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{
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lockdep_assert_held(&cgroup_mutex);
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if (css->flags & CSS_DYING)
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return;
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css->flags |= CSS_DYING;
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/*
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* This must happen before css is disassociated with its cgroup.
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* See seq_css() for details.
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@ -176,9 +176,9 @@ typedef enum {
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} cpuset_flagbits_t;
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/* convenient tests for these bits */
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static inline bool is_cpuset_online(const struct cpuset *cs)
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static inline bool is_cpuset_online(struct cpuset *cs)
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{
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return test_bit(CS_ONLINE, &cs->flags);
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return test_bit(CS_ONLINE, &cs->flags) && !css_is_dying(&cs->css);
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}
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static inline int is_cpu_exclusive(const struct cpuset *cs)
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