Commit a0acae0e authored by Tejun Heo's avatar Tejun Heo
Browse files

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

Documentation/power/freezing-of-tasks.txt

+6 −6
Original line number Diff line number Diff line
@@ -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?

drivers/net/irda/stir4200.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

fs/btrfs/async-thread.c

+1 −1
Original line number Diff line number Diff line
@@ -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()) {

fs/btrfs/disk-io.c

+2 −6
Original line number Diff line number Diff line
@@ -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))

fs/ext4/super.c

+1 −2
Original line number Diff line number Diff line
@@ -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)) ||

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