kernel/linux.git/include/linux/rcuwait.h, branch v6.19.11

types: move struct rcuwait into types.h

2025-03-17T05:06:18+00:00

Move rcuwait struct definition into types.h so that rcuwait can be used without including rcuwait.h which includes other headers. Without this change mm_types.h can't use rcuwait due to a the following circular dependency: mm_types.h -> rcuwait.h -> signal.h -> mm_types.h Link: https://lkml.kernel.org/r/20250213224655.1680278-7-surenb@google.com Suggested-by: Matthew Wilcox Signed-off-by: Suren Baghdasaryan Acked-by: Davidlohr Bueso Acked-by: Liam R. Howlett Acked-by: Lorenzo Stoakes Tested-by: Shivank Garg Link: https://lkml.kernel.org/r/5e19ec93-8307-47c2-bb13-3ddf7150624e@amd.com Cc: Christian Brauner Cc: David Hildenbrand Cc: David Howells Cc: Hugh Dickins Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Klara Modin Cc: Lokesh Gidra Cc: Mateusz Guzik Cc: Mel Gorman Cc: Michal Hocko Cc: Minchan Kim Cc: Oleg Nesterov Cc: Pasha Tatashin Cc: "Paul E . McKenney" Cc: Peter Xu Cc: Peter Zijlstra (Intel) Cc: Shakeel Butt Cc: Sourav Panda Cc: Vlastimil Babka Cc: Wei Yang Cc: Will Deacon Cc: Heiko Carstens Cc: Stephen Rothwell Signed-off-by: Andrew Morton

rcuwait: Support timeouts

2023-05-23T19:55:12+00:00

The rcuwait utility provides an efficient and safe single wait/wake mechanism. It is used in situations where queued wait is the wrong semantics, and often too bulky. For example, cases where the wait is already done under a lock. In the past, rcuwait has been extended to support beyond only uninterruptible sleep, and similarly, there are users that can benefit for the addition of timeouts. As such, tntroduce rcuwait_wait_event_timeout(), with semantics equivalent to calls for queued wait counterparts. Acked-by: Peter Zijlstra (Intel) Signed-off-by: Davidlohr Bueso Link: https://lore.kernel.org/r/20230523170927.20685-2-dave@stgolabs.net Signed-off-by: Dan Williams

rcu: Uninline multi-use function: finish_rcuwait()

2022-02-14T18:36:58+00:00

This is a rarely used function, so uninlining its 3 instructions is probably a win or a wash - but the main motivation is to make independent of task_struct details. Signed-off-by: Ingo Molnar Signed-off-by: Paul E. McKenney

rcuwait: avoid lockdep splats from rcuwait_active()

2020-05-20T07:39:40+00:00

rcuwait_active only returns whether w->task is not NULL. This is exactly one of the usecases that are mentioned in the documentation for rcu_access_pointer() where it is correct to bypass lockdep checks. This avoids a splat from kvm_vcpu_on_spin(). Reported-by: Wanpeng Li Tested-by: Wanpeng Li Acked-by: Davidlohr Bueso Cc: Peter Zijlstra Signed-off-by: Paolo Bonzini

rcuwait: Introduce rcuwait_active()

2020-05-13T16:14:54+00:00

This call is lockless and thus should not be trusted blindly. For example, the return value of rcuwait_wakeup() should be used to track whether a process was woken up. Signed-off-by: Davidlohr Bueso Message-Id: <20200424054837.5138-5-dave@stgolabs.net> Acked-by: Peter Zijlstra (Intel) Signed-off-by: Paolo Bonzini

rcuwait: Introduce prepare_to and finish_rcuwait

2020-05-13T16:14:53+00:00

This allows further flexibility for some callers to implement ad-hoc versions of the generic rcuwait_wait_event(). For example, kvm will need this to maintain tracing semantics. The naming is of course similar to what waitqueue apis offer. Also go ahead and make use of rcu_assign_pointer() for both task writes as it will make the __rcu sparse people happy - this will be the special nil case, thus no added serialization. Acked-by: Peter Zijlstra (Intel) Signed-off-by: Davidlohr Bueso Message-Id: <20200424054837.5138-4-dave@stgolabs.net> Signed-off-by: Paolo Bonzini

rcuwait: Let rcuwait_wake_up() return whether or not a task was awoken

2020-05-13T16:14:52+00:00

Propagating the return value of wake_up_process() back to the caller can come in handy for future users, such as for statistics or accounting purposes. Acked-by: Peter Zijlstra (Intel) Signed-off-by: Davidlohr Bueso Message-Id: <20200424054837.5138-3-dave@stgolabs.net> Signed-off-by: Paolo Bonzini

rcuwait: Add @state argument to rcuwait_wait_event()

2020-03-21T15:00:22+00:00

Extend rcuwait_wait_event() with a state variable so that it is not restricted to UNINTERRUPTIBLE waits. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200321113241.824030968@linutronix.de

tasks, sched/core: With a grace period after finish_task_switch(), remove unnecessary code

2019-09-25T15:42:29+00:00

Remove work arounds that were written before there was a grace period after tasks left the runqueue in finish_task_switch(). In particular now that there tasks exiting the runqueue exprience a RCU grace period none of the work performed by task_rcu_dereference() excpet the rcu_dereference() is necessary so replace task_rcu_dereference() with rcu_dereference(). Remove the code in rcuwait_wait_event() that checks to ensure the current task has not exited. It is no longer necessary as it is guaranteed that any running task will experience a RCU grace period after it leaves the run queueue. Remove the comment in rcuwait_wake_up() as it is no longer relevant. Ref: 8f95c90ceb54 ("sched/wait, RCU: Introduce rcuwait machinery") Ref: 150593bf8693 ("sched/api: Introduce task_rcu_dereference() and try_get_task_struct()") Signed-off-by: Eric W. Biederman Signed-off-by: Peter Zijlstra (Intel) Cc: Chris Metcalf Cc: Christoph Lameter Cc: Davidlohr Bueso Cc: Kirill Tkhai Cc: Linus Torvalds Cc: Mike Galbraith Cc: Oleg Nesterov Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Russell King - ARM Linux admin Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/87lfurdpk9.fsf_-_@x220.int.ebiederm.org Signed-off-by: Ingo Molnar

rcuwait: Annotate task_struct with __rcu

2019-04-03T10:34:31+00:00

This suppresses sparse error generated due to the recently added rcu_assign_pointer sparse check. percpu-rwsem.c:162:9: sparse: error: incompatible types in comparison expression exit.c:316:16: sparse: error: incompatible types in comparison expression Signed-off-by: Joel Fernandes (Google) Signed-off-by: Peter Zijlstra (Intel) [ From an RCU perspective. ] Reviewed-by: Paul E. McKenney Cc: Josh Triplett Cc: Lai Jiangshan Cc: Linus Torvalds Cc: Luc Van Oostenryck Cc: Mathieu Desnoyers Cc: Mike Galbraith Cc: Morten Rasmussen Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Cc: keescook@chromium.org Cc: kernel-hardening@lists.openwall.com Cc: kernel-team@android.com Link: https://lkml.kernel.org/r/20190321003426.160260-4-joel@joelfernandes.org Signed-off-by: Ingo Molnar