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charset="utf-8" Content-Transfer-Encoding: quoted-printable Binder allows you to freeze a process where some of its threads are blocked on the Binder driver. To make this work, we need to pass TASK_FREEZABLE when going to sleep in the appropriate places. Thus, add a new method wait_interruptible_freezable for the condition variable so that sleeps where this is supported can be marked as such. Signed-off-by: Alice Ryhl --- Changes in v2: - Document that you must not hold locks when you call the method. - Link to v1: https://lore.kernel.org/r/20250130-condvar-freeze-v1-1-a91d56= 61d505@google.com --- rust/kernel/sync/condvar.rs | 23 ++++++++++++++++++++++- rust/kernel/task.rs | 2 ++ 2 files changed, 24 insertions(+), 1 deletion(-) diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs index 7df565038d7d..1859e011e322 100644 --- a/rust/kernel/sync/condvar.rs +++ b/rust/kernel/sync/condvar.rs @@ -11,7 +11,9 @@ init::PinInit, pin_init, str::CStr, - task::{MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE, TASK_NORMAL, TASK_UNI= NTERRUPTIBLE}, + task::{ + MAX_SCHEDULE_TIMEOUT, TASK_FREEZABLE, TASK_INTERRUPTIBLE, TASK_NOR= MAL, TASK_UNINTERRUPTIBLE, + }, time::Jiffies, types::Opaque, }; @@ -159,6 +161,25 @@ pub fn wait_interruptible(&self= , guard: &mut Guard<'_, T, crate::current!().signal_pending() } =20 + /// Releases the lock and waits for a notification in interruptible an= d freezable mode. + /// + /// The process is allowed to be frozen during this sleep. You must no= t hold any locks while + /// this operation is ongoing, and there is a lockdep assertion for th= is. Freezing a task that + /// holds a lock can trivially deadlock vs another task that needs tha= t lock to complete before + /// it too can hit freezable. + #[must_use =3D "wait returns if a signal is pending, so the caller mus= t check the return value"] + pub fn wait_interruptible_freezable( + &self, + guard: &mut Guard<'_, T, B>, + ) -> bool { + self.wait_internal( + TASK_INTERRUPTIBLE | TASK_FREEZABLE, + guard, + MAX_SCHEDULE_TIMEOUT, + ); + crate::current!().signal_pending() + } + /// Releases the lock and waits for a notification in interruptible mo= de. /// /// Atomically releases the given lock (whose ownership is proven by t= he guard) and puts the diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs index 07bc22a7645c..ea43a3b8d9c5 100644 --- a/rust/kernel/task.rs +++ b/rust/kernel/task.rs @@ -23,6 +23,8 @@ pub const TASK_INTERRUPTIBLE: c_int =3D bindings::TASK_INTERRUPTIBLE as c_= int; /// Bitmask for tasks that are sleeping in an uninterruptible state. pub const TASK_UNINTERRUPTIBLE: c_int =3D bindings::TASK_UNINTERRUPTIBLE a= s c_int; +/// Bitmask for tasks that are sleeping in a freezable state. +pub const TASK_FREEZABLE: c_int =3D bindings::TASK_FREEZABLE as c_int; /// Convenience constant for waking up tasks regardless of whether they ar= e in interruptible or /// uninterruptible sleep. pub const TASK_NORMAL: c_uint =3D bindings::TASK_NORMAL as c_uint; --- base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b change-id: 20250130-condvar-freeze-f2ea5b308405 Best regards, --=20 Alice Ryhl