user/sven/linux.git/include/linux/seqlock.h, branch v6.9.5

locking/seqlock: Split out seqlock_types.h

2023-12-21T00:26:31Z

Trimming down sched.h dependencies: we don't want to include more than the base types. Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Signed-off-by: Kent Overstreet

locking/seqlock: Fix grammar in comment

2023-10-17T11:28:12Z

The "neither writes before and after ..." for the description of do_write_seqcount_end() should be "neither writes before nor after". Signed-off-by: Cuda-Chen Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20231017053703.11312-1-clh960524@gmail.com

locking/seqlock: Propagate 'const' pointers within read-only methods, remove forced type casts

2023-10-14T09:06:15Z

Currently __seqprop_ptr() is an inline function that must chose to either use 'const' or non-const seqcount related pointers - but this results in the undesirable loss of 'const' propagation, via a forced type cast. The easiest solution would be to turn the pointer wrappers into macros that pass through whatever type is passed to them - but the clever maze of seqlock API instantiation macros relies on the GCC CPP '##' macro extension, which isn't recursive, so inline functions must be used here. So create two wrapper variants instead: 'ptr' and 'const_ptr', and pick the right one for the codepaths that are const: read_seqcount_begin() and read_seqcount_retry(). This cleans up type handling and allows the removal of all type forcing. No change in functionality. Signed-off-by: Ingo Molnar Reviewed-by: Oleg Nesterov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Waiman Long Cc: Will Deacon Cc: Thomas Gleixner Cc: Paul E. McKenney

locking/seqlock: Change __seqprop() to return the function pointer

2023-10-12T18:18:21Z

This simplifies the macro and makes it easy to add the new seqprop's with 2 or more args. Plus this way we do not lose the type info, the (void*) type cast is no longer needed. And the latter reveals the problem: a lot of seqcount_t helpers pass the "const seqcount_t *s" argument to __seqprop_ptr(seqcount_t *s) but (before this patch) "(void *)(s)" masked the problem. So this patch changes __seqprop_ptr() and __seqprop_##lockname##_ptr() to accept the "const LOCKNAME *s" argument. This is not nice either, they need to drop the constness on return because these helpers are used by both the readers and writers, but at least it is clear what's going on. Signed-off-by: Oleg Nesterov Signed-off-by: Ingo Molnar Cc: Peter Zijlstra Cc: Waiman Long Cc: Will Deacon Cc: Thomas Gleixner Cc: Linus Torvalds Cc: Paul E. McKenney Link: https://lore.kernel.org/r/20231012143227.GA16143@redhat.com

locking/seqlock: Simplify SEQCOUNT_LOCKNAME()

2023-10-12T18:18:20Z

1. Kill the "lockmember" argument. It is always s->lock plus __seqprop_##lockname##_sequence() already uses s->lock and ignores "lockmember". 2. Kill the "lock_acquire" argument. __seqprop_##lockname##_sequence() can use the same "lockbase" prefix for _lock and _unlock. Apart from line numbers, gcc -E outputs the same code. Signed-off-by: Oleg Nesterov Signed-off-by: Ingo Molnar Cc: Peter Zijlstra Cc: Waiman Long Cc: Will Deacon Cc: Thomas Gleixner Cc: Linus Torvalds Cc: Paul E. McKenney Link: https://lore.kernel.org/r/20231012143158.GA16133@redhat.com

Merge tag 'v6.6-rc5' into locking/core, to pick up fixes

2023-10-09T16:09:23Z

Signed-off-by: Ingo Molnar

locking/seqlock: Fix typo in comment

2023-10-05T08:39:44Z

s/the the /the [ mingo: Cleaned up the changelog. ] Signed-off-by: Zizhen Pang Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/70293ecd5bb7a1cd370fd4d95c35f936@208suo.com

locking/seqlock: Do the lockdep annotation before locking in do_write_seqcount_begin_nested()

2023-09-21T06:37:44Z

It was brought up by Tetsuo that the following sequence: write_seqlock_irqsave() printk_deferred_enter() could lead to a deadlock if the lockdep annotation within write_seqlock_irqsave() triggers. The problem is that the sequence counter is incremented before the lockdep annotation is performed. The lockdep splat would then attempt to invoke printk() but the reader side, of the same seqcount, could have a tty_port::lock acquired waiting for the sequence number to become even again. The other lockdep annotations come before the actual locking because "we want to see the locking error before it happens". There is no reason why seqcount should be different here. Do the lockdep annotation first then perform the locking operation (the sequence increment). Fixes: 1ca7d67cf5d5a ("seqcount: Add lockdep functionality to seqcount/seqlock structures") Reported-by: Tetsuo Handa Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20230920104627._DTHgPyA@linutronix.de Closes: https://lore.kernel.org/20230621130641.-5iueY1I@linutronix.de

seqlock/latch: Provide raw_read_seqcount_latch_retry()

2023-06-05T19:11:03Z

The read side of seqcount_latch consists of: do { seq = raw_read_seqcount_latch(&latch->seq); ... } while (read_seqcount_latch_retry(&latch->seq, seq)); which is asymmetric in the raw_ department, and sure enough, read_seqcount_latch_retry() includes (explicit) instrumentation where raw_read_seqcount_latch() does not. This inconsistency becomes a problem when trying to use it from noinstr code. As such, fix it by renaming and re-implementing raw_read_seqcount_latch_retry() without the instrumentation. Specifically the instrumentation in question is kcsan_atomic_next(0) in do___read_seqcount_retry(). Loosing this annotation is not a problem because raw_read_seqcount_latch() does not pass through kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX). Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Reviewed-by: Petr Mladek Tested-by: Michael Kelley # Hyper-V Link: https://lore.kernel.org/r/20230519102715.233598176@infradead.org

seqlock: drop seqcount_ww_mutex_t

2022-04-07T10:53:54Z

Daniel pointed out that this series removes the last user of seqcount_ww_mutex_t, so let's drop this. Signed-off-by: Christian König Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: linux-kernel@vger.kernel.org Acked-by: Peter Zijlstra (Intel) Reviewed-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20220407085946.744568-16-christian.koenig@amd.com