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![Rafael J. Wysocki](/assets/img/avatar_default.png)
Commit2aede851dd
PM / Hibernate: Freeze kernel threads after preallocating memory introduced a mechanism by which kernel threads were frozen after the preallocation of hibernate image memory to avoid problems with frozen kernel threads not responding to memory freeing requests. However, it overlooked the s2disk code path in which the SNAPSHOT_CREATE_IMAGE ioctl was run directly after SNAPSHOT_FREE, which caused freeze_workqueues_begin() to BUG(), because it saw that worqueues had been already frozen. Although in principle this issue might be addressed by removing the relevant BUG_ON() from freeze_workqueues_begin(), that would reintroduce the very problem that commit2aede851dd
attempted to avoid into that particular code path. For this reason, to fix the issue at hand, introduce thaw_kernel_threads() and make the SNAPSHOT_FREE ioctl execute it. Special thanks to Srivatsa S. Bhat for detailed analysis of the problem. Reported-and-tested-by: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: stable@kernel.org
203 lines
5.8 KiB
C++
203 lines
5.8 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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#include <linux/atomic.h>
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#ifdef CONFIG_FREEZER
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extern atomic_t system_freezing_cnt; /* nr of freezing conds in effect */
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extern bool pm_freezing; /* PM freezing in effect */
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extern bool pm_nosig_freezing; /* PM nosig freezing in effect */
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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 bool 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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extern bool freezing_slow_path(struct task_struct *p);
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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 bool freezing(struct task_struct *p)
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{
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if (likely(!atomic_read(&system_freezing_cnt)))
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return false;
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return freezing_slow_path(p);
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}
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/* Takes and releases task alloc lock using task_lock() */
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extern void __thaw_task(struct task_struct *t);
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extern bool __refrigerator(bool check_kthr_stop);
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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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extern void thaw_kernel_threads(void);
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static inline bool try_to_freeze(void)
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{
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might_sleep();
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if (likely(!freezing(current)))
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return false;
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return __refrigerator(false);
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}
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extern bool freeze_task(struct task_struct *p);
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extern bool set_freezable(void);
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#ifdef CONFIG_CGROUP_FREEZER
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extern bool cgroup_freezing(struct task_struct *task);
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#else /* !CONFIG_CGROUP_FREEZER */
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static inline bool cgroup_freezing(struct task_struct *task)
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{
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return false;
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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. Fortunately, in the ____call_usermodehelper() case the
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* parent won't really block freeze_processes(), since ____call_usermodehelper()
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* (the child) does a little before exec/exit and it can't be frozen before
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* waking up the parent.
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*/
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/* Tell the freezer not to count the current task as freezable. */
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static inline void freezer_do_not_count(void)
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{
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current->flags |= PF_FREEZER_SKIP;
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}
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/*
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* Tell the freezer to count the current task as freezable again and try to
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* freeze it.
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*/
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static inline void freezer_count(void)
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{
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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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* 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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* These macros are intended to be used whenever you want allow a task that's
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* sleeping in TASK_UNINTERRUPTIBLE or TASK_KILLABLE state to be frozen. Note
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* that neither return any clear indication of whether a freeze event happened
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* while in this function.
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*/
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/* Like schedule(), but should not block the freezer. */
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#define freezable_schedule() \
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({ \
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freezer_do_not_count(); \
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schedule(); \
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freezer_count(); \
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})
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/* Like schedule_timeout_killable(), but should not block the freezer. */
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#define freezable_schedule_timeout_killable(timeout) \
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({ \
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long __retval; \
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freezer_do_not_count(); \
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__retval = schedule_timeout_killable(timeout); \
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freezer_count(); \
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__retval; \
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})
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/*
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* Freezer-friendly wrappers around wait_event_interruptible(),
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* wait_event_killable() and wait_event_interruptible_timeout(), originally
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* defined in <linux/wait.h>
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*/
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#define wait_event_freezekillable(wq, condition) \
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({ \
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int __retval; \
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freezer_do_not_count(); \
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__retval = wait_event_killable(wq, (condition)); \
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freezer_count(); \
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__retval; \
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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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for (;;) { \
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__retval = wait_event_interruptible(wq, \
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(condition) || freezing(current)); \
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if (__retval || (condition)) \
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break; \
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try_to_freeze(); \
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} \
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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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for (;;) { \
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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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if (__retval <= 0 || (condition)) \
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break; \
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try_to_freeze(); \
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} \
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__retval; \
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})
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#else /* !CONFIG_FREEZER */
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static inline bool frozen(struct task_struct *p) { return false; }
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static inline bool freezing(struct task_struct *p) { return false; }
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static inline void __thaw_task(struct task_struct *t) {}
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static inline bool __refrigerator(bool check_kthr_stop) { return false; }
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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 void thaw_kernel_threads(void) {}
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static inline bool try_to_freeze(void) { return false; }
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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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#define freezable_schedule() schedule()
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#define freezable_schedule_timeout_killable(timeout) \
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schedule_timeout_killable(timeout)
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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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#define wait_event_freezekillable(wq, condition) \
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wait_event_killable(wq, condition)
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#endif /* !CONFIG_FREEZER */
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#endif /* FREEZER_H_INCLUDED */
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