pm/sleep: Add PM_USERSPACE_AUTOSLEEP Kconfig

Systems that initiate frequent suspend/resume from userspace
can make the kernel aware by enabling PM_USERSPACE_AUTOSLEEP
config.

This allows for certain sleep-sensitive code (wireguard/rng) to
decide on what preparatory work should be performed (or not) in
their pm_notification callbacks.

This patch was prompted by the discussion at [1] which attempts
to remove CONFIG_ANDROID that currently guards these code paths.

[1] https://lore.kernel.org/r/20220629150102.1582425-1-hch@lst.de/

Suggested-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Link: https://lore.kernel.org/r/20220630191230.235306-1-kaleshsingh@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/char/random.c b/drivers/char/random.c
index e3dd1dd..8c90f53 100644 (file)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -755,8 +755,8 @@ static int random_pm_notification(struct notifier_block *nb, unsigned long actio
        spin_unlock_irqrestore(&input_pool.lock, flags);
 
        if (crng_ready() && (action == PM_RESTORE_PREPARE ||
-           (action == PM_POST_SUSPEND &&
-            !IS_ENABLED(CONFIG_PM_AUTOSLEEP) && !IS_ENABLED(CONFIG_ANDROID)))) {
+           (action == PM_POST_SUSPEND && !IS_ENABLED(CONFIG_PM_AUTOSLEEP) &&
+            !IS_ENABLED(CONFIG_PM_USERSPACE_AUTOSLEEP)))) {
                crng_reseed();
                pr_notice("crng reseeded on system resumption\n");
        }

diff --git a/drivers/net/wireguard/device.c b/drivers/net/wireguard/device.c
index aa9a7a5..d58e9f8 100644 (file)
--- a/drivers/net/wireguard/device.c
+++ b/drivers/net/wireguard/device.c
@@ -69,7 +69,8 @@ static int wg_pm_notification(struct notifier_block *nb, unsigned long action, v
         * its normal operation rather than as a somewhat rare event, then we
         * don't actually want to clear keys.
         */
-       if (IS_ENABLED(CONFIG_PM_AUTOSLEEP) || IS_ENABLED(CONFIG_ANDROID))
+       if (IS_ENABLED(CONFIG_PM_AUTOSLEEP) ||
+           IS_ENABLED(CONFIG_PM_USERSPACE_AUTOSLEEP))
                return 0;
 
        if (action != PM_HIBERNATION_PREPARE && action != PM_SUSPEND_PREPARE)

diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index a127796..60a1d30 100644 (file)
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -143,6 +143,26 @@ config PM_AUTOSLEEP
        Allow the kernel to trigger a system transition into a global sleep
        state automatically whenever there are no active wakeup sources.
 
+config PM_USERSPACE_AUTOSLEEP
+       bool "Userspace opportunistic sleep"
+       depends on PM_SLEEP
+       help
+       Notify kernel of aggressive userspace autosleep power management policy.
+
+       This option changes the behavior of various sleep-sensitive code to deal
+       with frequent userspace-initiated transitions into a global sleep state.
+
+       Saying Y here, disables code paths that most users really should keep
+       enabled. In particular, only enable this if it is very common to be
+       asleep/awake for very short periods of time (<= 2 seconds).
+
+       Only platforms, such as Android, that implement opportunistic sleep from
+       a userspace power manager service should enable this option; and not
+       other machines. Therefore, you should say N here, unless you are
+       extremely certain that this is what you want. The option otherwise has
+       bad, undesirable effects, and should not be enabled just for fun.
+
+
 config PM_WAKELOCKS
        bool "User space wakeup sources interface"
        depends on PM_SLEEP