Commit a0acae0e authored by Tejun Heo's avatar Tejun Heo

freezer: unexport refrigerator() and update try_to_freeze() slightly

There is no reason to export two functions for entering the
refrigerator.  Calling refrigerator() instead of try_to_freeze()
doesn't save anything noticeable or removes any race condition.

* Rename refrigerator() to __refrigerator() and make it return bool
  indicating whether it scheduled out for freezing.

* Update try_to_freeze() to return bool and relay the return value of
  __refrigerator() if freezing().

* Convert all refrigerator() users to try_to_freeze().

* Update documentation accordingly.

* While at it, add might_sleep() to try_to_freeze().
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Samuel Ortiz <samuel@sortiz.org>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: KONISHI Ryusuke <konishi.ryusuke@lab.ntt.co.jp>
Cc: Christoph Hellwig <hch@infradead.org>
parent 3a7cbd50
......@@ -21,7 +21,7 @@ freeze_processes() (defined in kernel/power/process.c) is called. It executes
try_to_freeze_tasks() that sets TIF_FREEZE for all of the freezable tasks and
either wakes them up, if they are kernel threads, or sends fake signals to them,
if they are user space processes. A task that has TIF_FREEZE set, should react
to it by calling the function called refrigerator() (defined in
to it by calling the function called __refrigerator() (defined in
kernel/freezer.c), which sets the task's PF_FROZEN flag, changes its state
to TASK_UNINTERRUPTIBLE and makes it loop until PF_FROZEN is cleared for it.
Then, we say that the task is 'frozen' and therefore the set of functions
......@@ -29,10 +29,10 @@ handling this mechanism is referred to as 'the freezer' (these functions are
defined in kernel/power/process.c, kernel/freezer.c & include/linux/freezer.h).
User space processes are generally frozen before kernel threads.
It is not recommended to call refrigerator() directly. Instead, it is
recommended to use the try_to_freeze() function (defined in
include/linux/freezer.h), that checks the task's TIF_FREEZE flag and makes the
task enter refrigerator() if the flag is set.
__refrigerator() must not be called directly. Instead, use the
try_to_freeze() function (defined in include/linux/freezer.h), that checks
the task's TIF_FREEZE flag and makes the task enter __refrigerator() if the
flag is set.
For user space processes try_to_freeze() is called automatically from the
signal-handling code, but the freezable kernel threads need to call it
......@@ -61,7 +61,7 @@ wait_event_freezable() and wait_event_freezable_timeout() macros.
After the system memory state has been restored from a hibernation image and
devices have been reinitialized, the function thaw_processes() is called in
order to clear the PF_FROZEN flag for each frozen task. Then, the tasks that
have been frozen leave refrigerator() and continue running.
have been frozen leave __refrigerator() and continue running.
III. Which kernel threads are freezable?
......
......@@ -750,7 +750,7 @@ static int stir_transmit_thread(void *arg)
write_reg(stir, REG_CTRL1, CTRL1_TXPWD|CTRL1_RXPWD);
refrigerator();
try_to_freeze();
if (change_speed(stir, stir->speed))
break;
......
......@@ -340,7 +340,7 @@ again:
if (freezing(current)) {
worker->working = 0;
spin_unlock_irq(&worker->lock);
refrigerator();
try_to_freeze();
} else {
spin_unlock_irq(&worker->lock);
if (!kthread_should_stop()) {
......
......@@ -1579,9 +1579,7 @@ static int cleaner_kthread(void *arg)
btrfs_run_defrag_inodes(root->fs_info);
}
if (freezing(current)) {
refrigerator();
} else {
if (!try_to_freeze()) {
set_current_state(TASK_INTERRUPTIBLE);
if (!kthread_should_stop())
schedule();
......@@ -1635,9 +1633,7 @@ sleep:
wake_up_process(root->fs_info->cleaner_kthread);
mutex_unlock(&root->fs_info->transaction_kthread_mutex);
if (freezing(current)) {
refrigerator();
} else {
if (!try_to_freeze()) {
set_current_state(TASK_INTERRUPTIBLE);
if (!kthread_should_stop() &&
!btrfs_transaction_blocked(root->fs_info))
......
......@@ -2882,8 +2882,7 @@ cont_thread:
}
mutex_unlock(&eli->li_list_mtx);
if (freezing(current))
refrigerator();
try_to_freeze();
cur = jiffies;
if ((time_after_eq(cur, next_wakeup)) ||
......
......@@ -951,8 +951,8 @@ int gfs2_logd(void *data)
wake_up(&sdp->sd_log_waitq);
t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;
if (freezing(current))
refrigerator();
try_to_freeze();
do {
prepare_to_wait(&sdp->sd_logd_waitq, &wait,
......
......@@ -1427,8 +1427,8 @@ int gfs2_quotad(void *data)
/* Check for & recover partially truncated inodes */
quotad_check_trunc_list(sdp);
if (freezing(current))
refrigerator();
try_to_freeze();
t = min(quotad_timeo, statfs_timeo);
prepare_to_wait(&sdp->sd_quota_wait, &wait, TASK_INTERRUPTIBLE);
......
......@@ -166,7 +166,7 @@ loop:
*/
jbd_debug(1, "Now suspending kjournald\n");
spin_unlock(&journal->j_state_lock);
refrigerator();
try_to_freeze();
spin_lock(&journal->j_state_lock);
} else {
/*
......
......@@ -173,7 +173,7 @@ loop:
*/
jbd_debug(1, "Now suspending kjournald2\n");
write_unlock(&journal->j_state_lock);
refrigerator();
try_to_freeze();
write_lock(&journal->j_state_lock);
} else {
/*
......
......@@ -2349,7 +2349,7 @@ int jfsIOWait(void *arg)
if (freezing(current)) {
spin_unlock_irq(&log_redrive_lock);
refrigerator();
try_to_freeze();
} else {
set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_irq(&log_redrive_lock);
......
......@@ -2800,7 +2800,7 @@ int jfs_lazycommit(void *arg)
if (freezing(current)) {
LAZY_UNLOCK(flags);
refrigerator();
try_to_freeze();
} else {
DECLARE_WAITQUEUE(wq, current);
......@@ -2994,7 +2994,7 @@ int jfs_sync(void *arg)
if (freezing(current)) {
TXN_UNLOCK();
refrigerator();
try_to_freeze();
} else {
set_current_state(TASK_INTERRUPTIBLE);
TXN_UNLOCK();
......
......@@ -2470,7 +2470,7 @@ static int nilfs_segctor_thread(void *arg)
if (freezing(current)) {
spin_unlock(&sci->sc_state_lock);
refrigerator();
try_to_freeze();
spin_lock(&sci->sc_state_lock);
} else {
DEFINE_WAIT(wait);
......
......@@ -1703,7 +1703,7 @@ xfsbufd(
if (unlikely(freezing(current))) {
set_bit(XBT_FORCE_SLEEP, &target->bt_flags);
refrigerator();
try_to_freeze();
} else {
clear_bit(XBT_FORCE_SLEEP, &target->bt_flags);
}
......
......@@ -47,18 +47,17 @@ static inline bool should_send_signal(struct task_struct *p)
/* Takes and releases task alloc lock using task_lock() */
extern int thaw_process(struct task_struct *p);
extern void refrigerator(void);
extern bool __refrigerator(void);
extern int freeze_processes(void);
extern int freeze_kernel_threads(void);
extern void thaw_processes(void);
static inline int try_to_freeze(void)
static inline bool try_to_freeze(void)
{
if (freezing(current)) {
refrigerator();
return 1;
} else
return 0;
might_sleep();
if (likely(!freezing(current)))
return false;
return __refrigerator();
}
extern bool freeze_task(struct task_struct *p, bool sig_only);
......@@ -181,12 +180,12 @@ static inline void set_freeze_flag(struct task_struct *p) {}
static inline void clear_freeze_flag(struct task_struct *p) {}
static inline int thaw_process(struct task_struct *p) { return 1; }
static inline void refrigerator(void) {}
static inline bool __refrigerator(void) { return false; }
static inline int freeze_processes(void) { return -ENOSYS; }
static inline int freeze_kernel_threads(void) { return -ENOSYS; }
static inline void thaw_processes(void) {}
static inline int try_to_freeze(void) { return 0; }
static inline bool try_to_freeze(void) { return false; }
static inline void freezer_do_not_count(void) {}
static inline void freezer_count(void) {}
......
......@@ -23,10 +23,11 @@ static inline void frozen_process(void)
}
/* Refrigerator is place where frozen processes are stored :-). */
void refrigerator(void)
bool __refrigerator(void)
{
/* Hmm, should we be allowed to suspend when there are realtime
processes around? */
bool was_frozen = false;
long save;
task_lock(current);
......@@ -35,7 +36,7 @@ void refrigerator(void)
task_unlock(current);
} else {
task_unlock(current);
return;
return was_frozen;
}
save = current->state;
pr_debug("%s entered refrigerator\n", current->comm);
......@@ -51,6 +52,7 @@ void refrigerator(void)
set_current_state(TASK_UNINTERRUPTIBLE);
if (!frozen(current))
break;
was_frozen = true;
schedule();
}
......@@ -65,8 +67,10 @@ void refrigerator(void)
* synchronization which depends on ordered task state change.
*/
set_current_state(save);
return was_frozen;
}
EXPORT_SYMBOL(refrigerator);
EXPORT_SYMBOL(__refrigerator);
static void fake_signal_wake_up(struct task_struct *p)
{
......
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