cgroup_freezer: make freezer->state mask of flags
freezer->state was an enum value - one of THAWED, FREEZING and FROZEN.
As the scheduled full hierarchy support requires more than one
freezing condition, switch it to mask of flags. If FREEZING is not
set, it's thawed. FREEZING is set if freezing or frozen. If frozen,
both FREEZING and FROZEN are set. Now that tasks can be attached to
an already frozen cgroup, this also makes freezing condition checks
more natural.
This patch doesn't introduce any behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 2690830..e76aa9f 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -22,15 +22,14 @@
#include <linux/freezer.h>
#include <linux/seq_file.h>
-enum freezer_state {
- CGROUP_THAWED = 0,
- CGROUP_FREEZING,
- CGROUP_FROZEN,
+enum freezer_state_flags {
+ CGROUP_FREEZING = (1 << 1), /* this freezer is freezing */
+ CGROUP_FROZEN = (1 << 3), /* this and its descendants frozen */
};
struct freezer {
struct cgroup_subsys_state css;
- enum freezer_state state;
+ unsigned int state;
spinlock_t lock;
};
@@ -48,12 +47,10 @@
bool cgroup_freezing(struct task_struct *task)
{
- enum freezer_state state;
bool ret;
rcu_read_lock();
- state = task_freezer(task)->state;
- ret = state == CGROUP_FREEZING || state == CGROUP_FROZEN;
+ ret = task_freezer(task)->state & CGROUP_FREEZING;
rcu_read_unlock();
return ret;
@@ -63,10 +60,13 @@
* cgroups_write_string() limits the size of freezer state strings to
* CGROUP_LOCAL_BUFFER_SIZE
*/
-static const char *freezer_state_strs[] = {
- "THAWED",
- "FREEZING",
- "FROZEN",
+static const char *freezer_state_strs(unsigned int state)
+{
+ if (state & CGROUP_FROZEN)
+ return "FROZEN";
+ if (state & CGROUP_FREEZING)
+ return "FREEZING";
+ return "THAWED";
};
/*
@@ -91,7 +91,6 @@
return ERR_PTR(-ENOMEM);
spin_lock_init(&freezer->lock);
- freezer->state = CGROUP_THAWED;
return &freezer->css;
}
@@ -99,7 +98,7 @@
{
struct freezer *freezer = cgroup_freezer(cgroup);
- if (freezer->state != CGROUP_THAWED)
+ if (freezer->state & CGROUP_FREEZING)
atomic_dec(&system_freezing_cnt);
kfree(freezer);
}
@@ -129,15 +128,13 @@
* Tasks in @tset are on @new_cgrp but may not conform to its
* current state before executing the following - !frozen tasks may
* be visible in a FROZEN cgroup and frozen tasks in a THAWED one.
- * This means that, to determine whether to freeze, one should test
- * whether the state equals THAWED.
*/
cgroup_taskset_for_each(task, new_cgrp, tset) {
- if (freezer->state == CGROUP_THAWED) {
+ if (!(freezer->state & CGROUP_FREEZING)) {
__thaw_task(task);
} else {
freeze_task(task);
- freezer->state = CGROUP_FREEZING;
+ freezer->state &= ~CGROUP_FROZEN;
}
}
@@ -159,11 +156,7 @@
goto out;
spin_lock_irq(&freezer->lock);
- /*
- * @task might have been just migrated into a FROZEN cgroup. Test
- * equality with THAWED. Read the comment in freezer_attach().
- */
- if (freezer->state != CGROUP_THAWED)
+ if (freezer->state & CGROUP_FREEZING)
freeze_task(task);
spin_unlock_irq(&freezer->lock);
out:
@@ -184,7 +177,8 @@
struct cgroup_iter it;
struct task_struct *task;
- if (freezer->state != CGROUP_FREEZING)
+ if (!(freezer->state & CGROUP_FREEZING) ||
+ (freezer->state & CGROUP_FROZEN))
return;
cgroup_iter_start(cgroup, &it);
@@ -202,7 +196,7 @@
}
}
- freezer->state = CGROUP_FROZEN;
+ freezer->state |= CGROUP_FROZEN;
notyet:
cgroup_iter_end(cgroup, &it);
}
@@ -211,14 +205,14 @@
struct seq_file *m)
{
struct freezer *freezer = cgroup_freezer(cgroup);
- enum freezer_state state;
+ unsigned int state;
spin_lock_irq(&freezer->lock);
update_if_frozen(freezer);
state = freezer->state;
spin_unlock_irq(&freezer->lock);
- seq_puts(m, freezer_state_strs[state]);
+ seq_puts(m, freezer_state_strs(state));
seq_putc(m, '\n');
return 0;
}
@@ -258,14 +252,14 @@
lockdep_assert_held(&freezer->lock);
if (freeze) {
- if (freezer->state == CGROUP_THAWED)
+ if (!(freezer->state & CGROUP_FREEZING))
atomic_inc(&system_freezing_cnt);
- freezer->state = CGROUP_FREEZING;
+ freezer->state |= CGROUP_FREEZING;
freeze_cgroup(freezer);
} else {
- if (freezer->state != CGROUP_THAWED)
+ if (freezer->state & CGROUP_FREEZING)
atomic_dec(&system_freezing_cnt);
- freezer->state = CGROUP_THAWED;
+ freezer->state &= ~(CGROUP_FREEZING | CGROUP_FROZEN);
unfreeze_cgroup(freezer);
}
}
@@ -290,9 +284,9 @@
{
bool freeze;
- if (strcmp(buffer, freezer_state_strs[CGROUP_THAWED]) == 0)
+ if (strcmp(buffer, freezer_state_strs(0)) == 0)
freeze = false;
- else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
+ else if (strcmp(buffer, freezer_state_strs(CGROUP_FROZEN)) == 0)
freeze = true;
else
return -EINVAL;