Message ID | d05a1c0c-1212-17f4-3772-042e2ff76a40@freesources.org (mailing list archive) |
---|---|
State | Mainlined, archived |
Headers | show |
Series | [v3] PM: suspend: Add sysfs attribute to control the "sync on suspend" behavior | expand |
On Thu, Jan 16, 2020 at 12:53 PM Jonas Meurer <jonas@freesources.org> wrote: > > The sysfs attribute `/sys/power/sync_on_suspend` controls, whether or not > filesystems are synced by the kernel before system suspend. > > Congruously, the behaviour of build-time switch CONFIG_SUSPEND_SKIP_SYNC > is slightly changed: It now defines the run-tim default for the new sysfs > attribute `/sys/power/sync_on_suspend`. > > The run-time attribute is added because the existing corresponding > build-time Kconfig flag for (`CONFIG_SUSPEND_SKIP_SYNC`) is not flexible > enough. E.g. Linux distributions that provide pre-compiled kernels > usually want to stick with the default (sync filesystems before suspend) > but under special conditions this needs to be changed. > > One example for such a special condition is user-space handling of > suspending block devices (e.g. using `cryptsetup luksSuspend` or `dmsetup > suspend`) before system suspend. The Kernel trying to sync filesystems > after the underlying block device already got suspended obviously leads > to dead-locks. Be aware that you have to take care of the filesystem sync > yourself before suspending the system in those scenarios. > > Signed-off-by: Jonas Meurer <jonas@freesources.org> Applied as 5.6 material with minor changes in the ABI document, thanks! > --- > Documentation/ABI/testing/sysfs-power | 13 +++++++++++ > include/linux/suspend.h | 2 ++ > kernel/power/Kconfig | 5 +++- > kernel/power/main.c | 33 +++++++++++++++++++++++++++ > kernel/power/suspend.c | 2 +- > 5 files changed, 53 insertions(+), 2 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power > index 6f87b9dd384b..9392a83afce8 100644 > --- a/Documentation/ABI/testing/sysfs-power > +++ b/Documentation/ABI/testing/sysfs-power > @@ -407,3 +407,16 @@ Contact: Kalesh Singh <kaleshsingh96@gmail.com> > Description: > The /sys/power/suspend_stats/last_failed_step file contains > the last failed step in the suspend/resume path. > + > +What: /sys/power/sync_on_suspend > +Date: October 2019 > +Contact: Jonas Meurer <jonas@freesources.org> > +Description: > + This file controls whether or not the kernel will sync() > + filesystems during system suspend (after freezing user space > + and before suspending devices). > + > + Writing a "1" to this file enables the sync() and writing a > + "0" disables it. Reads from the file return the current value. > + The default is "1" but can be configured with the build-time > + config flag "SUSPEND_SKIP_SYNC". > diff --git a/include/linux/suspend.h b/include/linux/suspend.h > index 6fc8843f1c9e..4a230c2f1c31 100644 > --- a/include/linux/suspend.h > +++ b/include/linux/suspend.h > @@ -329,6 +329,7 @@ extern void arch_suspend_disable_irqs(void); > extern void arch_suspend_enable_irqs(void); > > extern int pm_suspend(suspend_state_t state); > +extern bool sync_on_suspend_enabled; > #else /* !CONFIG_SUSPEND */ > #define suspend_valid_only_mem NULL > > @@ -342,6 +343,7 @@ static inline bool pm_suspend_default_s2idle(void) { return false; } > > static inline void suspend_set_ops(const struct platform_suspend_ops *ops) {} > static inline int pm_suspend(suspend_state_t state) { return -ENOSYS; } > +static inline bool sync_on_suspend_enabled(void) { return true; } > static inline bool idle_should_enter_s2idle(void) { return false; } > static inline void __init pm_states_init(void) {} > static inline void s2idle_set_ops(const struct platform_s2idle_ops *ops) {} > diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig > index d3667b4075c1..7cbfbeacd68a 100644 > --- a/kernel/power/Kconfig > +++ b/kernel/power/Kconfig > @@ -27,7 +27,10 @@ config SUSPEND_SKIP_SYNC > Skip the kernel sys_sync() before freezing user processes. > Some systems prefer not to pay this cost on every invocation > of suspend, or they are content with invoking sync() from > - user-space before invoking suspend. Say Y if that's your case. > + user-space before invoking suspend. There's a run-time switch > + at '/sys/power/sync_on_suspend' to configure this behaviour. > + This setting changes the default for the run-tim switch. Say Y > + to change the default to disable the kernel sys_sync(). > > config HIBERNATE_CALLBACKS > bool > diff --git a/kernel/power/main.c b/kernel/power/main.c > index e26de7af520b..69b7a8aeca3b 100644 > --- a/kernel/power/main.c > +++ b/kernel/power/main.c > @@ -190,6 +190,38 @@ static ssize_t mem_sleep_store(struct kobject *kobj, struct kobj_attribute *attr > } > > power_attr(mem_sleep); > + > +/* > + * sync_on_suspend: invoke ksys_sync_helper() before suspend. > + * > + * show() returns whether ksys_sync_helper() is invoked before suspend. > + * store() accepts 0 or 1. 0 disables ksys_sync_helper() and 1 enables it. > + */ > +bool sync_on_suspend_enabled = !IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC); > + > +static ssize_t sync_on_suspend_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + return sprintf(buf, "%d\n", sync_on_suspend_enabled); > +} > + > +static ssize_t sync_on_suspend_store(struct kobject *kobj, > + struct kobj_attribute *attr, > + const char *buf, size_t n) > +{ > + unsigned long val; > + > + if (kstrtoul(buf, 10, &val)) > + return -EINVAL; > + > + if (val > 1) > + return -EINVAL; > + > + sync_on_suspend_enabled = !!val; > + return n; > +} > + > +power_attr(sync_on_suspend); > #endif /* CONFIG_SUSPEND */ > > #ifdef CONFIG_PM_SLEEP_DEBUG > @@ -855,6 +887,7 @@ static struct attribute * g[] = { > &wakeup_count_attr.attr, > #ifdef CONFIG_SUSPEND > &mem_sleep_attr.attr, > + &sync_on_suspend_attr.attr, > #endif > #ifdef CONFIG_PM_AUTOSLEEP > &autosleep_attr.attr, > diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c > index f3b7239f1892..2c47280fbfc7 100644 > --- a/kernel/power/suspend.c > +++ b/kernel/power/suspend.c > @@ -564,7 +564,7 @@ static int enter_state(suspend_state_t state) > if (state == PM_SUSPEND_TO_IDLE) > s2idle_begin(); > > - if (!IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC)) { > + if (sync_on_suspend_enabled) { > trace_suspend_resume(TPS("sync_filesystems"), 0, true); > ksys_sync_helper(); > trace_suspend_resume(TPS("sync_filesystems"), 0, false); > -- > 2.20.1 >
Hey Rafael, Rafael J. Wysocki: > On Thu, Jan 16, 2020 at 12:53 PM Jonas Meurer <jonas@freesources.org> wrote: >> >> The sysfs attribute `/sys/power/sync_on_suspend` controls, whether or not >> filesystems are synced by the kernel before system suspend. >> >> Congruously, the behaviour of build-time switch CONFIG_SUSPEND_SKIP_SYNC >> is slightly changed: It now defines the run-tim default for the new sysfs >> attribute `/sys/power/sync_on_suspend`. >> >> The run-time attribute is added because the existing corresponding >> build-time Kconfig flag for (`CONFIG_SUSPEND_SKIP_SYNC`) is not flexible >> enough. E.g. Linux distributions that provide pre-compiled kernels >> usually want to stick with the default (sync filesystems before suspend) >> but under special conditions this needs to be changed. >> >> One example for such a special condition is user-space handling of >> suspending block devices (e.g. using `cryptsetup luksSuspend` or `dmsetup >> suspend`) before system suspend. The Kernel trying to sync filesystems >> after the underlying block device already got suspended obviously leads >> to dead-locks. Be aware that you have to take care of the filesystem sync >> yourself before suspending the system in those scenarios. >> >> Signed-off-by: Jonas Meurer <jonas@freesources.org> > > Applied as 5.6 material with minor changes in the ABI document, thanks! Wow, that's great news. I'm excited to read that the patch finally will enter the Linux kernel \o/ Thanks a lot for guiding me through my first Linux kernel patch contribution. Cheers jonas
Hi! > > The sysfs attribute `/sys/power/sync_on_suspend` controls, whether or not > > filesystems are synced by the kernel before system suspend. > > > > Congruously, the behaviour of build-time switch CONFIG_SUSPEND_SKIP_SYNC > > is slightly changed: It now defines the run-tim default for the new sysfs > > attribute `/sys/power/sync_on_suspend`. > > > > The run-time attribute is added because the existing corresponding > > build-time Kconfig flag for (`CONFIG_SUSPEND_SKIP_SYNC`) is not flexible > > enough. E.g. Linux distributions that provide pre-compiled kernels > > usually want to stick with the default (sync filesystems before suspend) > > but under special conditions this needs to be changed. > > > > One example for such a special condition is user-space handling of > > suspending block devices (e.g. using `cryptsetup luksSuspend` or `dmsetup > > suspend`) before system suspend. The Kernel trying to sync filesystems > > after the underlying block device already got suspended obviously leads > > to dead-locks. Be aware that you have to take care of the filesystem sync > > yourself before suspending the system in those scenarios. > > > > Signed-off-by: Jonas Meurer <jonas@freesources.org> > > Applied as 5.6 material with minor changes in the ABI document, thanks! For the record, I still believe this is bad idea. User should not have to tweak variables in /sys for system not to deadlock with cryptsetup.. and we are stuck with this pretty much forever. Pavel
diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power index 6f87b9dd384b..9392a83afce8 100644 --- a/Documentation/ABI/testing/sysfs-power +++ b/Documentation/ABI/testing/sysfs-power @@ -407,3 +407,16 @@ Contact: Kalesh Singh <kaleshsingh96@gmail.com> Description: The /sys/power/suspend_stats/last_failed_step file contains the last failed step in the suspend/resume path. + +What: /sys/power/sync_on_suspend +Date: October 2019 +Contact: Jonas Meurer <jonas@freesources.org> +Description: + This file controls whether or not the kernel will sync() + filesystems during system suspend (after freezing user space + and before suspending devices). + + Writing a "1" to this file enables the sync() and writing a + "0" disables it. Reads from the file return the current value. + The default is "1" but can be configured with the build-time + config flag "SUSPEND_SKIP_SYNC". diff --git a/include/linux/suspend.h b/include/linux/suspend.h index 6fc8843f1c9e..4a230c2f1c31 100644 --- a/include/linux/suspend.h +++ b/include/linux/suspend.h @@ -329,6 +329,7 @@ extern void arch_suspend_disable_irqs(void); extern void arch_suspend_enable_irqs(void); extern int pm_suspend(suspend_state_t state); +extern bool sync_on_suspend_enabled; #else /* !CONFIG_SUSPEND */ #define suspend_valid_only_mem NULL @@ -342,6 +343,7 @@ static inline bool pm_suspend_default_s2idle(void) { return false; } static inline void suspend_set_ops(const struct platform_suspend_ops *ops) {} static inline int pm_suspend(suspend_state_t state) { return -ENOSYS; } +static inline bool sync_on_suspend_enabled(void) { return true; } static inline bool idle_should_enter_s2idle(void) { return false; } static inline void __init pm_states_init(void) {} static inline void s2idle_set_ops(const struct platform_s2idle_ops *ops) {} diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig index d3667b4075c1..7cbfbeacd68a 100644 --- a/kernel/power/Kconfig +++ b/kernel/power/Kconfig @@ -27,7 +27,10 @@ config SUSPEND_SKIP_SYNC Skip the kernel sys_sync() before freezing user processes. Some systems prefer not to pay this cost on every invocation of suspend, or they are content with invoking sync() from - user-space before invoking suspend. Say Y if that's your case. + user-space before invoking suspend. There's a run-time switch + at '/sys/power/sync_on_suspend' to configure this behaviour. + This setting changes the default for the run-tim switch. Say Y + to change the default to disable the kernel sys_sync(). config HIBERNATE_CALLBACKS bool diff --git a/kernel/power/main.c b/kernel/power/main.c index e26de7af520b..69b7a8aeca3b 100644 --- a/kernel/power/main.c +++ b/kernel/power/main.c @@ -190,6 +190,38 @@ static ssize_t mem_sleep_store(struct kobject *kobj, struct kobj_attribute *attr } power_attr(mem_sleep); + +/* + * sync_on_suspend: invoke ksys_sync_helper() before suspend. + * + * show() returns whether ksys_sync_helper() is invoked before suspend. + * store() accepts 0 or 1. 0 disables ksys_sync_helper() and 1 enables it. + */ +bool sync_on_suspend_enabled = !IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC); + +static ssize_t sync_on_suspend_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%d\n", sync_on_suspend_enabled); +} + +static ssize_t sync_on_suspend_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t n) +{ + unsigned long val; + + if (kstrtoul(buf, 10, &val)) + return -EINVAL; + + if (val > 1) + return -EINVAL; + + sync_on_suspend_enabled = !!val; + return n; +} + +power_attr(sync_on_suspend); #endif /* CONFIG_SUSPEND */ #ifdef CONFIG_PM_SLEEP_DEBUG @@ -855,6 +887,7 @@ static struct attribute * g[] = { &wakeup_count_attr.attr, #ifdef CONFIG_SUSPEND &mem_sleep_attr.attr, + &sync_on_suspend_attr.attr, #endif #ifdef CONFIG_PM_AUTOSLEEP &autosleep_attr.attr, diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c index f3b7239f1892..2c47280fbfc7 100644 --- a/kernel/power/suspend.c +++ b/kernel/power/suspend.c @@ -564,7 +564,7 @@ static int enter_state(suspend_state_t state) if (state == PM_SUSPEND_TO_IDLE) s2idle_begin(); - if (!IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC)) { + if (sync_on_suspend_enabled) { trace_suspend_resume(TPS("sync_filesystems"), 0, true); ksys_sync_helper(); trace_suspend_resume(TPS("sync_filesystems"), 0, false);
The sysfs attribute `/sys/power/sync_on_suspend` controls, whether or not filesystems are synced by the kernel before system suspend. Congruously, the behaviour of build-time switch CONFIG_SUSPEND_SKIP_SYNC is slightly changed: It now defines the run-tim default for the new sysfs attribute `/sys/power/sync_on_suspend`. The run-time attribute is added because the existing corresponding build-time Kconfig flag for (`CONFIG_SUSPEND_SKIP_SYNC`) is not flexible enough. E.g. Linux distributions that provide pre-compiled kernels usually want to stick with the default (sync filesystems before suspend) but under special conditions this needs to be changed. One example for such a special condition is user-space handling of suspending block devices (e.g. using `cryptsetup luksSuspend` or `dmsetup suspend`) before system suspend. The Kernel trying to sync filesystems after the underlying block device already got suspended obviously leads to dead-locks. Be aware that you have to take care of the filesystem sync yourself before suspending the system in those scenarios. Signed-off-by: Jonas Meurer <jonas@freesources.org> --- Documentation/ABI/testing/sysfs-power | 13 +++++++++++ include/linux/suspend.h | 2 ++ kernel/power/Kconfig | 5 +++- kernel/power/main.c | 33 +++++++++++++++++++++++++++ kernel/power/suspend.c | 2 +- 5 files changed, 53 insertions(+), 2 deletions(-)