cgroup: use bitmask to filter for_each_subsys (cb4a3167) · Commits · 戴 / test

include/linux/cgroup-defs.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -490,6 +490,8 @@ static inline void cgroup_threadgroup_change_end(struct task_struct *tsk)

		#else /* CONFIG_CGROUPS */

		#define CGROUP_SUBSYS_COUNT 0

		static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk) {}
		static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {}

kernel/cgroup.c

+33 −20

Original line number	Diff line number	Diff line
		@@ -178,12 +178,13 @@ static DEFINE_IDR(cgroup_hierarchy_idr);
		*/
		static u64 css_serial_nr_next = 1;

		/* This flag indicates whether tasks in the fork and exit paths should
		* check for fork/exit handlers to call. This avoids us having to do
		* extra work in the fork/exit path if none of the subsystems need to
		* be called.
		/*
		* These bitmask flags indicate whether tasks in the fork and exit paths have
		* fork/exit handlers to call. This avoids us having to do extra work in the
		* fork/exit path to check which subsystems have fork/exit callbacks.
		*/
		static int need_forkexit_callback __read_mostly;
		static unsigned long have_fork_callback __read_mostly;
		static unsigned long have_exit_callback __read_mostly;

		static struct cftype cgroup_dfl_base_files[];
		static struct cftype cgroup_legacy_base_files[];
		@@ -412,6 +413,24 @@ static int notify_on_release(const struct cgroup *cgrp)
		for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
		(((ss) = cgroup_subsys[ssid]) \|\| true); (ssid)++)

		/**
		* for_each_subsys_which - filter for_each_subsys with a bitmask
		* @ss: the iteration cursor
		* @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
		* @ss_maskp: a pointer to the bitmask
		*
		* The block will only run for cases where the ssid-th bit (1 << ssid) of
		* mask is set to 1.
		*/
		#define for_each_subsys_which(ss, ssid, ss_maskp) \
		if (!CGROUP_SUBSYS_COUNT) /* to avoid spurious gcc warning */ \
		; \
		else \
		for_each_set_bit(ssid, ss_maskp, CGROUP_SUBSYS_COUNT) \
		if (((ss) = cgroup_subsys[ssid]) && false) \
		break; \
		else

		/* iterate across the hierarchies */
		#define for_each_root(root) \
		list_for_each_entry((root), &cgroup_roots, root_list)
		@@ -4914,7 +4933,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
		* init_css_set is in the subsystem's root cgroup. */
		init_css_set.subsys[ss->id] = css;

		need_forkexit_callback \|= ss->fork \|\| ss->exit;
		have_fork_callback \|= (bool)ss->fork << ss->id;
		have_exit_callback \|= (bool)ss->exit << ss->id;

		/* At system boot, before all subsystems have been
		* registered, no tasks have been forked, so we don't
		@@ -5225,12 +5245,9 @@ void cgroup_post_fork(struct task_struct *child)
		* css_set; otherwise, @child might change state between ->fork()
		* and addition to css_set.
		*/
		if (need_forkexit_callback) {
		for_each_subsys(ss, i)
		if (ss->fork)
		for_each_subsys_which(ss, i, &have_fork_callback)
		ss->fork(child);
		}
		}

		/**
		* cgroup_exit - detach cgroup from exiting task
		@@ -5273,17 +5290,13 @@ void cgroup_exit(struct task_struct *tsk)
		cset = task_css_set(tsk);
		RCU_INIT_POINTER(tsk->cgroups, &init_css_set);

		if (need_forkexit_callback) {
		/* see cgroup_post_fork() for details */
		for_each_subsys(ss, i) {
		if (ss->exit) {
		for_each_subsys_which(ss, i, &have_exit_callback) {
		struct cgroup_subsys_state *old_css = cset->subsys[i];
		struct cgroup_subsys_state *css = task_css(tsk, i);

		ss->exit(css, old_css, tsk);
		}
		}
		}

		if (put_cset)
		put_css_set(cset);

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