freezer: clean up freeze_processes() failure path

freeze_processes() failure path is rather messy.  Freezing is canceled
for workqueues and tasks which aren't frozen yet but frozen tasks are
left alone and should be thawed by the caller and of course some
callers (xen and kexec) didn't do it.

This patch updates __thaw_task() to handle cancelation correctly and
makes freeze_processes() and freeze_kernel_threads() call
thaw_processes() on failure instead so that the system is fully thawed
on failure.  Unnecessary [suspend_]thaw_processes() calls are removed
from kernel/power/hibernate.c, suspend.c and user.c.

While at it, restructure error checking if clause in suspend_prepare()
to be less weird.

-v2: Srivatsa spotted missing removal of suspend_thaw_processes() in
     suspend_prepare() and error in commit message.  Updated.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index ba4f512d29386d29385a1c9c664bfd66fbb9eba0..93f411a52872cafe071b4c4de9d9c936062e20c7 100644 (file)
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -61,7 +61,6 @@ static inline bool try_to_freeze(void)
 }
 
 extern bool freeze_task(struct task_struct *p, bool sig_only);
-extern void cancel_freezing(struct task_struct *p);
 
 #ifdef CONFIG_CGROUP_FREEZER
 extern int cgroup_freezing_or_frozen(struct task_struct *task);

diff --git a/kernel/freezer.c b/kernel/freezer.c
index b8b562124ba916e4dbedaca229f896e80efa5aef..11e32d419dec625a760eeba149546265eb51013b 100644 (file)
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -129,21 +129,6 @@ out_unlock:
        return ret;
 }
 
-void cancel_freezing(struct task_struct *p)
-{
-       unsigned long flags;
-
-       spin_lock_irqsave(&freezer_lock, flags);
-       if (freezing(p)) {
-               pr_debug("  clean up: %s\n", p->comm);
-               clear_freeze_flag(p);
-               spin_lock(&p->sighand->siglock);
-               recalc_sigpending_and_wake(p);
-               spin_unlock(&p->sighand->siglock);
-       }
-       spin_unlock_irqrestore(&freezer_lock, flags);
-}
-
 void __thaw_task(struct task_struct *p)
 {
        unsigned long flags;
@@ -153,10 +138,18 @@ void __thaw_task(struct task_struct *p)
         * be visible to @p as waking up implies wmb.  Waking up inside
         * freezer_lock also prevents wakeups from leaking outside
         * refrigerator.
+        *
+        * If !FROZEN, @p hasn't reached refrigerator, recalc sigpending to
+        * avoid leaving dangling TIF_SIGPENDING behind.
         */
        spin_lock_irqsave(&freezer_lock, flags);
        clear_freeze_flag(p);
-       if (frozen(p))
+       if (frozen(p)) {
                wake_up_process(p);
+       } else {
+               spin_lock(&p->sighand->siglock);
+               recalc_sigpending_and_wake(p);
+               spin_unlock(&p->sighand->siglock);
+       }
        spin_unlock_irqrestore(&freezer_lock, flags);
 }

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 196c01268ebd73d50c0a5f4d52d913c9aff8bd8b..ba2319ffc8601ed0a511893d2ab663321fa5952c 100644 (file)
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -607,17 +607,6 @@ static void power_down(void)
        while(1);
 }
 
-static int prepare_processes(void)
-{
-       int error = 0;
-
-       if (freeze_processes()) {
-               error = -EBUSY;
-               thaw_processes();
-       }
-       return error;
-}
-
 /**
  * hibernate - Carry out system hibernation, including saving the image.
  */
@@ -650,7 +639,7 @@ int hibernate(void)
        sys_sync();
        printk("done.\n");
 
-       error = prepare_processes();
+       error = freeze_processes();
        if (error)
                goto Finish;
 
@@ -811,7 +800,7 @@ static int software_resume(void)
                goto close_finish;
 
        pr_debug("PM: Preparing processes for restore.\n");
-       error = prepare_processes();
+       error = freeze_processes();
        if (error) {
                swsusp_close(FMODE_READ);
                goto Done;

diff --git a/kernel/power/process.c b/kernel/power/process.c
index e59676f5811d85f1d03a4934e36c2c56d48436c4..ce643838a00c687ec3ede41eb4ec3f6efb717fc9 100644 (file)
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -91,11 +91,6 @@ static int try_to_freeze_tasks(bool sig_only)
        elapsed_csecs = elapsed_csecs64;
 
        if (todo) {
-               /* This does not unfreeze processes that are already frozen
-                * (we have slightly ugly calling convention in that respect,
-                * 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 %s after %d.%02d seconds "
                       "(%d tasks refusing to freeze, wq_busy=%d):\n",
@@ -103,14 +98,11 @@ static int try_to_freeze_tasks(bool sig_only)
                       elapsed_csecs / 100, elapsed_csecs % 100,
                       todo - wq_busy, wq_busy);
 
-               thaw_workqueues();
-
                read_lock(&tasklist_lock);
                do_each_thread(g, p) {
                        if (!wakeup && !freezer_should_skip(p) &&
                            freezing(p) && !frozen(p))
                                sched_show_task(p);
-                       cancel_freezing(p);
                } while_each_thread(g, p);
                read_unlock(&tasklist_lock);
        } else {
@@ -123,6 +115,8 @@ static int try_to_freeze_tasks(bool sig_only)
 
 /**
  * freeze_processes - Signal user space processes to enter the refrigerator.
+ *
+ * On success, returns 0.  On failure, -errno and system is fully thawed.
  */
 int freeze_processes(void)
 {
@@ -137,11 +131,15 @@ int freeze_processes(void)
        printk("\n");
        BUG_ON(in_atomic());
 
+       if (error)
+               thaw_processes();
        return error;
 }
 
 /**
  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
+ *
+ * On success, returns 0.  On failure, -errno and system is fully thawed.
  */
 int freeze_kernel_threads(void)
 {
@@ -155,6 +153,8 @@ int freeze_kernel_threads(void)
        printk("\n");
        BUG_ON(in_atomic());
 
+       if (error)
+               thaw_processes();
        return error;
 }
 

diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 4953dc054c53c2af14ca9af22e5f64394feaf244..d336b27d1104fb5aa7aceff18c1742166325cf6d 100644 (file)
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -106,13 +106,11 @@ static int suspend_prepare(void)
                goto Finish;
 
        error = suspend_freeze_processes();
-       if (error) {
-               suspend_stats.failed_freeze++;
-               dpm_save_failed_step(SUSPEND_FREEZE);
-       } else
+       if (!error)
                return 0;
 
-       suspend_thaw_processes();
+       suspend_stats.failed_freeze++;
+       dpm_save_failed_step(SUSPEND_FREEZE);
        usermodehelper_enable();
  Finish:
        pm_notifier_call_chain(PM_POST_SUSPEND);

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 6d8f535c2b88e11952b3871ecb88d8fa0378ab40..7cc3f5bc5c24801365a4fafe4ddbcb0154baf5f9 100644 (file)
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -257,10 +257,8 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
                        break;
 
                error = freeze_processes();
-               if (error) {
-                       thaw_processes();
+               if (error)
                        usermodehelper_enable();
-               }
                if (!error)
                        data->frozen = 1;
                break;