kernel/linux.git/include/linux/rwsem.h, branch v6.12.80

locking: Make rwsem_assert_held_write_nolockdep() build with PREEMPT_RT=y

2024-04-08T14:39:16+00:00

The commit cited below broke the build for PREEMPT_RT because rwsem_assert_held_write_nolockdep() passes a struct rw_semaphore but rw_base_assert_held_write() expects struct rwbase_rt. Fixing the type alone leads to the problem that WARN_ON() is not found because bug.h is missing. In order to resolve this: - Keep the assert (WARN_ON()) in rwsem.h (not rwbase_rt.h) - Make rwsem_assert_held_write_nolockdep() do the implementation specific (rw_base) writer check. - Replace the "inline" with __always_inline which was used before. Fixes: f70405afc99b1 ("locking: Add rwsem_assert_held() and rwsem_assert_held_write()") Reported-by: Clark Williams Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Reviewed-by: Waiman Long Link: https://lore.kernel.org/r/20240319182050.U4AzUF3I@linutronix.de

locking: Add rwsem_assert_held() and rwsem_assert_held_write()

2024-02-19T15:49:33+00:00

Modelled after lockdep_assert_held() and lockdep_assert_held_write(), but are always active, even when lockdep is disabled. Of course, they don't test that _this_ thread is the owner, but it's sufficient to catch many bugs and doesn't incur the same performance penalty as lockdep. Acked-by: "Peter Zijlstra (Intel)" Acked-by: Waiman Long Acked-by: "Darrick J. Wong" Reviewed-by: Dave Chinner Signed-off-by: "Matthew Wilcox (Oracle)" Signed-off-by: Chandan Babu R

cleanup: Add conditional guard support

2023-11-15T09:15:33+00:00

Adds: - DEFINE_GUARD_COND() / DEFINE_LOCK_GUARD_1_COND() to extend existing guards with conditional lock primitives, eg. mutex_trylock(), mutex_lock_interruptible(). nb. both primitives allow NULL 'locks', which cause the lock to fail (obviously). - extends scoped_guard() to not take the body when the the conditional guard 'fails'. eg. scoped_guard (mutex_intr, &task->signal_cred_guard_mutex) { ... } will only execute the body when the mutex is held. - provides scoped_cond_guard(name, fail, args...); which extends scoped_guard() to do fail when the lock-acquire fails. Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20231102110706.460851167%40infradead.org

locking: Introduce __cleanup() based infrastructure

2023-06-26T09:14:18+00:00

Use __attribute__((__cleanup__(func))) to build: - simple auto-release pointers using __free() - 'classes' with constructor and destructor semantics for scope-based resource management. - lock guards based on the above classes. Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230612093537.614161713%40infradead.org

locking/rwsem: drop redundant semicolon of down_write_nest_lock

2022-01-14T10:08:37+00:00

Otherwise, braces are needed when using it. Signed-off-by: Guchun Chen Acked-by: Christian König Acked-by: Peter Zijlstra (Intel) Link: https://patchwork.freedesktop.org/patch/msgid/20220114083742.6219-1-guchun.chen@amd.com Signed-off-by: Christian König

kernel.h: drop unneeded inclusion from other headers

2021-11-09T18:02:49+00:00

Patch series "kernel.h further split", v5. kernel.h is a set of something which is not related to each other and often used in non-crossed compilation units, especially when drivers need only one or two macro definitions from it. This patch (of 7): There is no evidence we need kernel.h inclusion in certain headers. Drop unneeded inclusion from other headers. [sfr@canb.auug.org.au: bottom_half.h needs kernel] Link: https://lkml.kernel.org/r/20211015202908.1c417ae2@canb.auug.org.au Link: https://lkml.kernel.org/r/20211013170417.87909-1-andriy.shevchenko@linux.intel.com Link: https://lkml.kernel.org/r/20211013170417.87909-2-andriy.shevchenko@linux.intel.com Signed-off-by: Andy Shevchenko Signed-off-by: Stephen Rothwell Cc: Thomas Gleixner Cc: Brendan Higgins Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: Sakari Ailus Cc: Laurent Pinchart Cc: Mauro Carvalho Chehab Cc: Miguel Ojeda Cc: Jonathan Cameron Cc: Rasmus Villemoes Cc: Thorsten Leemhuis Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

locking/rwsem: Add missing __init_rwsem() for PREEMPT_RT

2021-09-02T20:07:17+00:00

730633f0b7f95 became the first direct caller of __init_rwsem() vs the usual init_rwsem(), exposing PREEMPT_RT's lack thereof. Add it. [ tglx: Move it out of line ] Signed-off-by: Mike Galbraith Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/50a936b7d8f12277d6ec7ed2ef0421a381056909.camel@gmx.de

locking/rwsem: Add rtmutex based R/W semaphore implementation

2021-08-17T15:12:47+00:00

The RT specific R/W semaphore implementation used to restrict the number of readers to one, because a writer cannot block on multiple readers and inherit its priority or budget. The single reader restricting was painful in various ways: - Performance bottleneck for multi-threaded applications in the page fault path (mmap sem) - Progress blocker for drivers which are carefully crafted to avoid the potential reader/writer deadlock in mainline. The analysis of the writer code paths shows that properly written RT tasks should not take them. Syscalls like mmap(), file access which take mmap sem write locked have unbound latencies, which are completely unrelated to mmap sem. Other R/W sem users like graphics drivers are not suitable for RT tasks either. So there is little risk to hurt RT tasks when the RT rwsem implementation is done in the following way: - Allow concurrent readers - Make writers block until the last reader left the critical section. This blocking is not subject to priority/budget inheritance. - Readers blocked on a writer inherit their priority/budget in the normal way. There is a drawback with this scheme: R/W semaphores become writer unfair though the applications which have triggered writer starvation (mostly on mmap_sem) in the past are not really the typical workloads running on a RT system. So while it's unlikely to hit writer starvation, it's possible. If there are unexpected workloads on RT systems triggering it, the problem has to be revisited. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20210815211303.016885947@linutronix.de

locking: Fix typos in comments

2021-03-22T01:45:52+00:00

Fix ~16 single-word typos in locking code comments. Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Paul E. McKenney Cc: Will Deacon Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar

rwsem: Implement down_read_interruptible

2020-12-09T16:08:42+00:00

In preparation for converting exec_update_mutex to a rwsem so that multiple readers can execute in parallel and not deadlock, add down_read_interruptible. This is needed for perf_event_open to be converted (with no semantic changes) from working on a mutex to wroking on a rwsem. Signed-off-by: Eric W. Biederman Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/87k0tybqfy.fsf@x220.int.ebiederm.org