![Rafael J. Wysocki](/assets/img/avatar_default.png)
There is a problem with the current ordering of hibernate code which leads to deadlocks in some filesystems' memory shrinkers. Namely, some filesystems use freezable kernel threads that are inactive when the hibernate memory preallocation is carried out. Those same filesystems use memory shrinkers that may be triggered by the hibernate memory preallocation. If those memory shrinkers wait for the frozen kernel threads, the hibernate process deadlocks (this happens with XFS, for one example). Apparently, it is not technically viable to redesign the filesystems in question to avoid the situation described above, so the only possible solution of this issue is to defer the freezing of kernel threads until the hibernate memory preallocation is done, which is implemented by this change. Unfortunately, this requires the memory preallocation to be done before the "prepare" stage of device freeze, so after this change the only way drivers can allocate additional memory for their freeze routines in a clean way is to use PM notifiers. Reported-by: Christoph <cr2005@u-club.de> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
196 lines
5.3 KiB
C++
196 lines
5.3 KiB
C++
/* Freezer declarations */
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#ifndef FREEZER_H_INCLUDED
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#define FREEZER_H_INCLUDED
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#include <linux/sched.h>
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#include <linux/wait.h>
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#ifdef CONFIG_FREEZER
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/*
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* Check if a process has been frozen
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*/
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static inline int frozen(struct task_struct *p)
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{
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return p->flags & PF_FROZEN;
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}
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/*
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* Check if there is a request to freeze a process
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*/
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static inline int freezing(struct task_struct *p)
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{
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return test_tsk_thread_flag(p, TIF_FREEZE);
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}
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/*
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* Request that a process be frozen
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*/
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static inline void set_freeze_flag(struct task_struct *p)
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{
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set_tsk_thread_flag(p, TIF_FREEZE);
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}
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/*
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* Sometimes we may need to cancel the previous 'freeze' request
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*/
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static inline void clear_freeze_flag(struct task_struct *p)
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{
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clear_tsk_thread_flag(p, TIF_FREEZE);
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}
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static inline bool should_send_signal(struct task_struct *p)
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{
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return !(p->flags & PF_FREEZER_NOSIG);
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}
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/* Takes and releases task alloc lock using task_lock() */
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extern int thaw_process(struct task_struct *p);
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extern void refrigerator(void);
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extern int freeze_processes(void);
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extern int freeze_kernel_threads(void);
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extern void thaw_processes(void);
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static inline int try_to_freeze(void)
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{
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if (freezing(current)) {
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refrigerator();
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return 1;
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} else
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return 0;
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}
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extern bool freeze_task(struct task_struct *p, bool sig_only);
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extern void cancel_freezing(struct task_struct *p);
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#ifdef CONFIG_CGROUP_FREEZER
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extern int cgroup_freezing_or_frozen(struct task_struct *task);
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#else /* !CONFIG_CGROUP_FREEZER */
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static inline int cgroup_freezing_or_frozen(struct task_struct *task)
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{
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return 0;
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}
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#endif /* !CONFIG_CGROUP_FREEZER */
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/*
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* The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
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* calls wait_for_completion(&vfork) and reset right after it returns from this
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* function. Next, the parent should call try_to_freeze() to freeze itself
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* appropriately in case the child has exited before the freezing of tasks is
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* complete. However, we don't want kernel threads to be frozen in unexpected
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* places, so we allow them to block freeze_processes() instead or to set
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* PF_NOFREEZE if needed and PF_FREEZER_SKIP is only set for userland vfork
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* parents. Fortunately, in the ____call_usermodehelper() case the parent won't
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* really block freeze_processes(), since ____call_usermodehelper() (the child)
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* does a little before exec/exit and it can't be frozen before waking up the
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* parent.
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*/
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/*
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* If the current task is a user space one, tell the freezer not to count it as
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* freezable.
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*/
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static inline void freezer_do_not_count(void)
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{
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if (current->mm)
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current->flags |= PF_FREEZER_SKIP;
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}
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/*
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* If the current task is a user space one, tell the freezer to count it as
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* freezable again and try to freeze it.
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*/
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static inline void freezer_count(void)
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{
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if (current->mm) {
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current->flags &= ~PF_FREEZER_SKIP;
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try_to_freeze();
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}
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}
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/*
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* Check if the task should be counted as freezable by the freezer
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*/
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static inline int freezer_should_skip(struct task_struct *p)
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{
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return !!(p->flags & PF_FREEZER_SKIP);
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}
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/*
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* Tell the freezer that the current task should be frozen by it
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*/
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static inline void set_freezable(void)
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{
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current->flags &= ~PF_NOFREEZE;
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}
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/*
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* Tell the freezer that the current task should be frozen by it and that it
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* should send a fake signal to the task to freeze it.
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*/
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static inline void set_freezable_with_signal(void)
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{
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current->flags &= ~(PF_NOFREEZE | PF_FREEZER_NOSIG);
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}
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/*
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* Freezer-friendly wrappers around wait_event_interruptible() and
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* wait_event_interruptible_timeout(), originally defined in <linux/wait.h>
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*/
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#define wait_event_freezable(wq, condition) \
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({ \
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int __retval; \
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do { \
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__retval = wait_event_interruptible(wq, \
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(condition) || freezing(current)); \
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if (__retval && !freezing(current)) \
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break; \
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else if (!(condition)) \
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__retval = -ERESTARTSYS; \
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} while (try_to_freeze()); \
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__retval; \
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})
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#define wait_event_freezable_timeout(wq, condition, timeout) \
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({ \
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long __retval = timeout; \
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do { \
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__retval = wait_event_interruptible_timeout(wq, \
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(condition) || freezing(current), \
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__retval); \
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} while (try_to_freeze()); \
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__retval; \
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})
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#else /* !CONFIG_FREEZER */
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static inline int frozen(struct task_struct *p) { return 0; }
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static inline int freezing(struct task_struct *p) { return 0; }
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static inline void set_freeze_flag(struct task_struct *p) {}
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static inline void clear_freeze_flag(struct task_struct *p) {}
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static inline int thaw_process(struct task_struct *p) { return 1; }
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static inline void refrigerator(void) {}
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static inline int freeze_processes(void) { return -ENOSYS; }
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static inline int freeze_kernel_threads(void) { return -ENOSYS; }
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static inline void thaw_processes(void) {}
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static inline int try_to_freeze(void) { return 0; }
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static inline void freezer_do_not_count(void) {}
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static inline void freezer_count(void) {}
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static inline int freezer_should_skip(struct task_struct *p) { return 0; }
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static inline void set_freezable(void) {}
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static inline void set_freezable_with_signal(void) {}
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#define wait_event_freezable(wq, condition) \
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wait_event_interruptible(wq, condition)
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#define wait_event_freezable_timeout(wq, condition, timeout) \
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wait_event_interruptible_timeout(wq, condition, timeout)
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#endif /* !CONFIG_FREEZER */
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#endif /* FREEZER_H_INCLUDED */
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