Development discussion of WireGuard
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From: Kalesh Singh <kaleshsingh@google.com>
To: Jason@zx2c4.com, jstultz@google.com, paulmck@kernel.org,
	 rostedt@goodmis.org, rafael@kernel.org, hch@infradead.org
Cc: saravanak@google.com, tjmercier@google.com, surenb@google.com,
	 kernel-team@android.com, Kalesh Singh <kaleshsingh@google.com>,
	 "Theodore Ts'o" <tytso@mit.edu>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	 Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>, Len Brown <len.brown@intel.com>,
	 Pavel Machek <pavel@ucw.cz>,
	linux-kernel@vger.kernel.org, wireguard@lists.zx2c4.com,
	 netdev@vger.kernel.org, linux-pm@vger.kernel.org
Subject: [PATCH] pm/sleep: Add PM_USERSPACE_AUTOSLEEP Kconfig
Date: Thu, 30 Jun 2022 19:12:29 +0000	[thread overview]
Message-ID: <20220630191230.235306-1-kaleshsingh@google.com> (raw)

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>
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 drivers/char/random.c          |  4 ++--
 drivers/net/wireguard/device.c |  3 ++-
 kernel/power/Kconfig           | 20 ++++++++++++++++++++
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index e3dd1dd3dd22..8c90f535d149 100644
--- 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 aa9a7a5970fd..d58e9f818d3b 100644
--- 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 a12779650f15..60a1d3051cc7 100644
--- 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

base-commit: 03c765b0e3b4cb5063276b086c76f7a612856a9a
-- 
2.37.0.rc0.161.g10f37bed90-goog


             reply	other threads:[~2022-06-30 19:12 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-30 19:12 Kalesh Singh [this message]
2022-06-30 19:49 ` Jason A. Donenfeld
2022-06-30 20:41   ` Kalesh Singh
2022-06-30 21:14     ` Jason A. Donenfeld
2022-06-30 22:02       ` Kalesh Singh
2022-06-30 22:08         ` Jason A. Donenfeld
2022-07-01  8:38   ` Greg KH

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