linux/kernel/power/suspend.c, branch v6.17

PM: suspend: clean up redundant filesystems_freeze/thaw() handling

2025-07-15T12:55:00Z

The recently introduced support for freezing filesystems during system suspend included calls to filesystems_freeze() in both suspend_prepare() and enter_state(), as well as calls to filesystems_thaw() in both suspend_finish() and the Unlock path in enter_state(). These are redundant. Moreover, calling filesystems_freeze() twice, from both suspend_prepare() and enter_state(), leads to a black screen and makes the system unable to resume in some cases. Address this as follows: - filesystems_freeze() is already called in suspend_prepare(), which is the proper and consistent place to handle pre-suspend operations. The second call in enter_state() is unnecessary and so remove it. - filesystems_thaw() is invoked in suspend_finish(), which covers successful suspend/resume paths. In the failure case, add a call to filesystems_thaw() only when needed, avoiding the duplicate call in the general Unlock path. This change simplifies the suspend code and avoids repeated freeze/thaw calls, while preserving correct ordering and behavior. Fixes: eacfbf74196f ("power: freeze filesystems during suspend/resume") Signed-off-by: Zihuan Zhang Link: https://patch.msgid.link/20250712030824.81474-1-zhangzihuan@kylinos.cn [ rjw: Changelog edits ] Signed-off-by: Rafael J. Wysocki

PM: suspend: Drop a misplaced pm_restore_gfp_mask() call

2025-07-15T12:54:26Z

The pm_restore_gfp_mask() call added by commit 12ffc3b1513e ("PM: Restrict swap use to later in the suspend sequence") to suspend_devices_and_enter() is done too early because it takes place before calling dpm_resume() in dpm_resume_end() and some swap-backing devices may not be ready at that point. Moreover, dpm_resume_end() called subsequently in the same code path invokes pm_restore_gfp_mask() again and calling it twice in a row is pointless. Drop the misplaced pm_restore_gfp_mask() call from suspend_devices_and_enter() to address this issue. Fixes: 12ffc3b1513e ("PM: Restrict swap use to later in the suspend sequence") Signed-off-by: Rafael J. Wysocki Reviewed-by: Mario Limonciello Link: https://patch.msgid.link/2810409.mvXUDI8C0e@rjwysocki.net [ rjw: Changelog edits ] Signed-off-by: Rafael J. Wysocki

PM: Restrict swap use to later in the suspend sequence

2025-06-26T18:39:34Z

Currently swap is restricted before drivers have had a chance to do their prepare() PM callbacks. Restricting swap this early means that if a driver needs to evict some content from memory into sawp in it's prepare callback, it won't be able to. On AMD dGPUs this can lead to failed suspends under memory pressure situations as all VRAM must be evicted to system memory or swap. Move the swap restriction to right after all devices have had a chance to do the prepare() callback. If there is any problem with the sequence, restore swap in the appropriate dpm resume callbacks or error handling paths. Closes: https://github.com/ROCm/ROCK-Kernel-Driver/issues/174 Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/2362 Signed-off-by: Mario Limonciello Tested-by: Nat Wittstock Tested-by: Lucian Langa Link: https://patch.msgid.link/20250613214413.4127087-1-superm1@kernel.org Signed-off-by: Rafael J. Wysocki

power: freeze filesystems during suspend/resume

2025-05-09T10:41:23Z

Now all the pieces are in place to actually allow the power subsystem to freeze/thaw filesystems during suspend/resume. Filesystems are only frozen and thawed if the power subsystem does actually own the freeze. We could bubble up errors and fail suspend/resume if the error isn't EBUSY (aka it's already frozen) but I don't think that this is worth it. Filesystem freezing during suspend/resume is best-effort. If the user has 500 ext4 filesystems mounted and 4 fail to freeze for whatever reason then we simply skip them. What we have now is already a big improvement and let's see how we fare with it before making our lives even harder (and uglier) than we have to. We add a new sysctl know /sys/power/freeze_filesystems that will allow userspace to freeze filesystems during suspend/hibernate. For now it defaults to off. The thaw logic doesn't require checking whether freezing is enabled because the power subsystem exclusively owns frozen filesystems for the duration of suspend/hibernate and is able to skip filesystems it doesn't need to freeze. Also it is technically possible that filesystem filesystem_freeze_enabled is true and power freezes the filesystems but before freezing all processes another process disables filesystem_freeze_enabled. If power were to place the filesystems_thaw() call under filesystems_freeze_enabled it would fail to thaw the fileystems it frozw. The exclusive holder mechanism makes it possible to iterate through the list without any concern making sure that no filesystems are left frozen. Link: https://lore.kernel.org/r/20250402-work-freeze-v2-3-6719a97b52ac@kernel.org Signed-off-by: Christian Brauner

Merge tag 'printk-for-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2025-03-28T02:22:24Z

Pull printk updates from Petr Mladek: - New option "printk.debug_non_panic_cpus" allows to store printk messages from non-panic CPUs during panic. It might be useful when panic() fails. It is disabled by default because it increases the chance to see the messages printed before panic() and on the panic-CPU. - New build option "CONFIG_NULL_TTY_DEFAULT_CONSOLE" allows to build kernel without the virtual terminal support which prefers ttynull over serial console. - Do not unblank suspended consoles. - Some code clean up. * tag 'printk-for-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: printk/panic: Add option to allow non-panic CPUs to write to the ring buffer. printk: Add an option to allow ttynull to be a default console device printk: Check CON_SUSPEND when unblanking a console printk: Rename console_start to console_resume printk: Rename console_stop to console_suspend printk: Rename resume_console to console_resume_all printk: Rename suspend_console to console_suspend_all

PM: s2idle: Extend comment in s2idle_enter()

2025-03-12T20:14:53Z

The s2idle_lock must be held while checking for a pending wakeup and while moving into S2IDLE_STATE_ENTER, to make sure a wakeup doesn't get lost. Let's extend the comment in the code to make this clear. Signed-off-by: Ulf Hansson Link: https://patch.msgid.link/20250311160827.1129643-3-ulf.hansson@linaro.org [ rjw: Rewrote the new comment ] Signed-off-by: Rafael J. Wysocki

PM: s2idle: Drop redundant locks when entering s2idle

2025-03-12T20:14:53Z

The calls to cpus_read_lock|unlock() protects us from getting CPUS hotplugged, while entering suspend-to-idle. However, when s2idle_enter() is called we should be far beyond the point when CPUs may be hotplugged. Let's therefore simplify the code and drop the use of the lock. Signed-off-by: Ulf Hansson Link: https://patch.msgid.link/20250311160827.1129643-2-ulf.hansson@linaro.org [ rjw: Rewrote the new comment ] Signed-off-by: Rafael J. Wysocki

printk: Rename resume_console to console_resume_all

2025-03-11T10:51:27Z

The function resume_console has a misleading name, since it resumes all consoles, so rename it accordingly. Signed-off-by: Marcos Paulo de Souza Reviewed-by: Petr Mladek Reviewed-by: John Ogness Link: https://lore.kernel.org/r/20250226-printk-renaming-v1-2-0b878577f2e6@suse.com [pmladek@suse.com: Fixed typo in the commit message.] Signed-off-by: Petr Mladek

printk: Rename suspend_console to console_suspend_all

2025-03-11T10:49:34Z

The function suspend_console has a misleading name, since it suspends all consoles, so rename it accordingly. Signed-off-by: Marcos Paulo de Souza Reviewed-by: Petr Mladek Reviewed-by: John Ogness Link: https://lore.kernel.org/r/20250226-printk-renaming-v1-1-0b878577f2e6@suse.com [pmladek@suse.com: Fixed typo in the commit message.] Signed-off-by: Petr Mladek

PM: s2idle: Make sure CPUs will wakeup directly on resume

2024-04-08T13:36:54Z

s2idle works like a regular suspend with freezing processes and freezing devices. All CPUs except the control CPU go into idle. Once this is completed the control CPU kicks all other CPUs out of idle, so that they reenter the idle loop and then enter s2idle state. The control CPU then issues an swait() on the suspend state and therefore enters the idle loop as well. Due to being kicked out of idle, the other CPUs leave their NOHZ states, which means the tick is active and the corresponding hrtimer is programmed to the next jiffie. On entering s2idle the CPUs shut down their local clockevent device to prevent wakeups. The last CPU which enters s2idle shuts down its local clockevent and freezes timekeeping. On resume, one of the CPUs receives the wakeup interrupt, unfreezes timekeeping and its local clockevent and starts the resume process. At that point all other CPUs are still in s2idle with their clockevents switched off. They only resume when they are kicked by another CPU or after resuming devices and then receiving a device interrupt. That means there is no guarantee that all CPUs will wakeup directly on resume. As a consequence there is no guarantee that timers which are queued on those CPUs and should expire directly after resume, are handled. Also timer list timers which are remotely queued to one of those CPUs after resume will not result in a reprogramming IPI as the tick is active. Queueing a hrtimer will also not result in a reprogramming IPI because the first hrtimer event is already in the past. The recent introduction of the timer pull model (7ee988770326 ("timers: Implement the hierarchical pull model")) amplifies this problem, if the current migrator is one of the non woken up CPUs. When a non pinned timer list timer is queued and the queuing CPU goes idle, it relies on the still suspended migrator CPU to expire the timer which will happen by chance. The problem exists since commit 8d89835b0467 ("PM: suspend: Do not pause cpuidle in the suspend-to-idle path"). There the cpuidle_pause() call which in turn invoked a wakeup for all idle CPUs was moved to a later point in the resume process. This might not be reached or reached very late because it waits on a timer of a still suspended CPU. Address this by kicking all CPUs out of idle after the control CPU returns from swait() so that they resume their timers and restore consistent system state. Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218641 Fixes: 8d89835b0467 ("PM: suspend: Do not pause cpuidle in the suspend-to-idle path") Signed-off-by: Anna-Maria Behnsen Reviewed-by: Thomas Gleixner Tested-by: Mario Limonciello Cc: 5.16+ # 5.16+ Acked-by: Peter Zijlstra (Intel) Reviewed-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki