Commit ba7b2387 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents e543c8a9 41c25707

include/linux/cgroup-defs.h

+1 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ enum { 
	CSS_ONLINE	= (1 << 1), /* between ->css_online() and ->css_offline() */

	CSS_RELEASED	= (1 << 2), /* refcnt reached zero, released */

	CSS_VISIBLE	= (1 << 3), /* css is visible to userland */

	CSS_DYING	= (1 << 4), /* css is dying */

};



/* bits in struct cgroup flags field */

include/linux/cgroup.h

+20 −0
Original line number Diff line number Diff line
@@ -343,6 +343,26 @@ static inline bool css_tryget_online(struct cgroup_subsys_state *css) 
	return true;

}



/**

 * css_is_dying - test whether the specified css is dying

 * @css: target css

 *

 * Test whether @css is in the process of offlining or already offline.  In

 * most cases, ->css_online() and ->css_offline() callbacks should be

 * enough; however, the actual offline operations are RCU delayed and this

 * test returns %true also when @css is scheduled to be offlined.

 *

 * This is useful, for example, when the use case requires synchronous

 * behavior with respect to cgroup removal.  cgroup removal schedules css

 * offlining but the css can seem alive while the operation is being

 * delayed.  If the delay affects user visible semantics, this test can be

 * used to resolve the situation.

 */

static inline bool css_is_dying(struct cgroup_subsys_state *css)

{

	return !(css->flags & CSS_NO_REF) && percpu_ref_is_dying(&css->refcnt);

}



/**

 * css_put - put a css reference

 * @css: target css

kernel/cgroup/cgroup.c

+5 −0
Original line number Diff line number Diff line
@@ -4265,6 +4265,11 @@ static void kill_css(struct cgroup_subsys_state *css) 
{

	lockdep_assert_held(&cgroup_mutex);



	if (css->flags & CSS_DYING)

		return;



	css->flags |= CSS_DYING;



	/*

	 * This must happen before css is disassociated with its cgroup.

	 * See seq_css() for details.

kernel/cgroup/cpuset.c

+2 −2
Original line number Diff line number Diff line
@@ -176,9 +176,9 @@ typedef enum { 
} cpuset_flagbits_t;



/* convenient tests for these bits */

static inline bool is_cpuset_online(const struct cpuset *cs)

static inline bool is_cpuset_online(struct cpuset *cs)

{

	return test_bit(CS_ONLINE, &cs->flags);

	return test_bit(CS_ONLINE, &cs->flags) && !css_is_dying(&cs->css);

}



static inline int is_cpu_exclusive(const struct cpuset *cs)

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