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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 <williams@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20240319182050.U4AzUF3I@linutronix.de
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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)" <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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On PREEMPT_RT, rw_semaphores and rwlocks are substituted with an rtmutex and
a reader count. The implementation is writer unfair, as it is not feasible
to do priority inheritance on multiple readers, but experience has shown
that real-time workloads are not the typical workloads which are sensitive
to writer starvation.
The inner workings of rw_semaphores and rwlocks on RT are almost identical
except for the task state and signal handling. rw_semaphores are not state
preserving over a contention, they are expected to enter and leave with state
== TASK_RUNNING. rwlocks have a mechanism to preserve the state of the task
at entry and restore it after unblocking taking potential non-lock related
wakeups into account. rw_semaphores can also be subject to signal handling
interrupting a blocked state, while rwlocks ignore signals.
To avoid code duplication, provide a shared implementation which takes the
small difference vs. state and signals into account. The code is included
into the relevant rw_semaphore/rwlock base code and compiled for each use
case separately.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.957920571@linutronix.de
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