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.
Unified · Split
| @@ -407,3 +407,16 @@ Contact: Kalesh Singh <kaleshsingh96@gmail.com> · 406 unmodified lines | ||
| 407 | 407 | Description: |
| 408 | 408 | The /sys/power/suspend_stats/last_failed_step file contains |
| 409 | 409 | the last failed step in the suspend/resume path. |
| 410 | + | |
| 411 | +What: /sys/power/sync_on_suspend | |
| 412 | +Date: October 2019 | |
| 413 | +Contact: Jonas Meurer <jonas@freesources.org> | |
| 414 | +Description: | |
| 415 | + This file controls whether or not the kernel will sync() | |
| 416 | + filesystems during system suspend (after freezing user space | |
| 417 | + and before suspending devices). | |
| 418 | + | |
| 419 | + Writing a "1" to this file enables the sync() and writing a "0" | |
| 420 | + disables it. Reads from the file return the current value. | |
| 421 | + The default is "1" if the build-time "SUSPEND_SKIP_SYNC" config | |
| 422 | + flag is unset, or "0" otherwise. | |
| @@ -329,6 +329,7 @@ extern void arch_suspend_disable_irqs(void); · 328 unmodified lines | ||
| 329 | 329 | extern void arch_suspend_enable_irqs(void); |
| 330 | 330 | |
| 331 | 331 | extern int pm_suspend(suspend_state_t state); |
| 332 | +extern bool sync_on_suspend_enabled; | |
| 332 | 333 | #else /* !CONFIG_SUSPEND */ |
| 333 | 334 | #define suspend_valid_only_mem NULL |
| 334 | 335 | |
| @@ -342,6 +343,7 @@ static inline bool pm_suspend_default_s2idle(void) { return false; } · 7 unmodified lines | ||
| 342 | 343 | |
| 343 | 344 | static inline void suspend_set_ops(const struct platform_suspend_ops *ops) {} |
| 344 | 345 | static inline int pm_suspend(suspend_state_t state) { return -ENOSYS; } |
| 346 | +static inline bool sync_on_suspend_enabled(void) { return true; } | |
| 345 | 347 | static inline bool idle_should_enter_s2idle(void) { return false; } |
| 346 | 348 | static inline void __init pm_states_init(void) {} |
| 347 | 349 | static inline void s2idle_set_ops(const struct platform_s2idle_ops *ops) {} |
| @@ -27,7 +27,10 @@ config SUSPEND_SKIP_SYNC · 26 unmodified lines | ||
| 27 | 27 | Skip the kernel sys_sync() before freezing user processes. |
| 28 | 28 | Some systems prefer not to pay this cost on every invocation |
| 29 | 29 | of suspend, or they are content with invoking sync() from |
| 30 | − user-space before invoking suspend. Say Y if that's your case. | |
| 30 | + user-space before invoking suspend. There's a run-time switch | |
| 31 | + at '/sys/power/sync_on_suspend' to configure this behaviour. | |
| 32 | + This setting changes the default for the run-tim switch. Say Y | |
| 33 | + to change the default to disable the kernel sys_sync(). | |
| 31 | 34 | |
| 32 | 35 | config HIBERNATE_CALLBACKS |
| 33 | 36 | bool |
| @@ -190,6 +190,38 @@ static ssize_t mem_sleep_store(struct kobject *kobj, struct kobj_attribute *attr · 189 unmodified lines | ||
| 190 | 190 | } |
| 191 | 191 | |
| 192 | 192 | power_attr(mem_sleep); |
| 193 | + | |
| 194 | +/* | |
| 195 | + * sync_on_suspend: invoke ksys_sync_helper() before suspend. | |
| 196 | + * | |
| 197 | + * show() returns whether ksys_sync_helper() is invoked before suspend. | |
| 198 | + * store() accepts 0 or 1. 0 disables ksys_sync_helper() and 1 enables it. | |
| 199 | + */ | |
| 200 | +bool sync_on_suspend_enabled = !IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC); | |
| 201 | + | |
| 202 | +static ssize_t sync_on_suspend_show(struct kobject *kobj, | |
| 203 | + struct kobj_attribute *attr, char *buf) | |
| 204 | +{ | |
| 205 | + return sprintf(buf, "%d\n", sync_on_suspend_enabled); | |
| 206 | +} | |
| 207 | + | |
| 208 | +static ssize_t sync_on_suspend_store(struct kobject *kobj, | |
| 209 | + struct kobj_attribute *attr, | |
| 210 | + const char *buf, size_t n) | |
| 211 | +{ | |
| 212 | + unsigned long val; | |
| 213 | + | |
| 214 | + if (kstrtoul(buf, 10, &val)) | |
| 215 | + return -EINVAL; | |
| 216 | + | |
| 217 | + if (val > 1) | |
| 218 | + return -EINVAL; | |
| 219 | + | |
| 220 | + sync_on_suspend_enabled = !!val; | |
| 221 | + return n; | |
| 222 | +} | |
| 223 | + | |
| 224 | +power_attr(sync_on_suspend); | |
| 193 | 225 | #endif /* CONFIG_SUSPEND */ |
| 194 | 226 | |
| 195 | 227 | #ifdef CONFIG_PM_SLEEP_DEBUG |
| @@ -855,6 +887,7 @@ static struct attribute * g[] = { · 659 unmodified lines | ||
| 855 | 887 | &wakeup_count_attr.attr, |
| 856 | 888 | #ifdef CONFIG_SUSPEND |
| 857 | 889 | &mem_sleep_attr.attr, |
| 890 | + &sync_on_suspend_attr.attr, | |
| 858 | 891 | #endif |
| 859 | 892 | #ifdef CONFIG_PM_AUTOSLEEP |
| 860 | 893 | &autosleep_attr.attr, |
| @@ -564,7 +564,7 @@ static int enter_state(suspend_state_t state) · 563 unmodified lines | ||
| 564 | 564 | if (state == PM_SUSPEND_TO_IDLE) |
| 565 | 565 | s2idle_begin(); |
| 566 | 566 | |
| 567 | − if (!IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC)) { | |
| 567 | + if (sync_on_suspend_enabled) { | |
| 568 | 568 | trace_suspend_resume(TPS("sync_filesystems"), 0, true); |
| 569 | 569 | ksys_sync_helper(); |
| 570 | 570 | trace_suspend_resume(TPS("sync_filesystems"), 0, false); |