[PATCH 04/10] PM: wakelock: Abort task freezing if a wakelock is locked.

Arve Hjønnevåg
2009-02-11T01:49:09Z

If a wakelock is locked, suspend will fail anyway. Since try_to_freeze_tasks
can take up to 20 seconds to complete or fail, aborting as soon as someone
locks a wakelock (e.g. from an interrupt handler) improves the worst case
wakeup latency.

On an older kernel where task freezing could fail for processes attached
to a debugger, this fixed a problem where the device sometimes hung for
20 seconds before the screen turned on.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
kernel/power/process.c | 22 +++++++++++++++++-----
1 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/kernel/power/process.c b/kernel/power/process.c
index ca63401..8388d01 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -13,6 +13,7 @@
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/freezer.h>
+#include <linux/wakelock.h>

/*
* Timeout for stopping processes
@@ -36,6 +37,7 @@ static int try_to_freeze_tasks(bool sig_only)
struct timeval start, end;
u64 elapsed_csecs64;
unsigned int elapsed_csecs;
+ unsigned int wakeup = 0;

do_gettimeofday(&start);

@@ -62,6 +64,10 @@ static int try_to_freeze_tasks(bool sig_only)
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
yield(); /* Yield is okay here */
+ if (todo && has_wake_lock(WAKE_LOCK_SUSPEND)) {
+ wakeup = 1;
+ break;
+ }
if (time_after(jiffies, end_time))
break;
} while (todo);
@@ -77,11 +83,17 @@ static int try_to_freeze_tasks(bool sig_only)
* and caller must call thaw_processes() if something fails),
* but it cleans up leftover PF_FREEZE requests.
*/
- printk("\n");
- printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
- "(%d tasks refusing to freeze):\n",
- elapsed_csecs / 100, elapsed_csecs % 100, todo);
- show_state();
+ if (wakeup) {
+ printk("\n");
+ printk(KERN_ERR "Freezing of %s aborted\n",
+ sig_only ? "user space " : "tasks ");
+ } else {
+ printk("\n");
+ printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
+ "(%d tasks refusing to freeze):\n",
+ elapsed_csecs / 100, elapsed_csecs % 100, todo);
+ show_state();
+ }
read_lock(&tasklist_lock);
do_each_thread(g, p) {
task_lock(p);
--
1.6.1

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