Adding debian version 6.1.76-1.debian/6.1.76-1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 63 insertions, 0 deletions

diff --git a/debian/patches-rt/0054-locking-rwbase-Mitigate-indefinite-writer-starvation.patch b/debian/patches-rt/0054-locking-rwbase-Mitigate-indefinite-writer-starvation.patch
new file mode 100644
index 000000000..1940c66d7
--- /dev/null
+++ b/debian/patches-rt/0054-locking-rwbase-Mitigate-indefinite-writer-starvation.patch
@@ -0,0 +1,63 @@
+From 8785dde5198dc91cbb518044e1c6d301ef9a9857 Mon Sep 17 00:00:00 2001
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Tue, 21 Mar 2023 17:11:40 +0100
+Subject: [PATCH 54/62] locking/rwbase: Mitigate indefinite writer starvation
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.1/older/patches-6.1.69-rt21.tar.xz
+
+On PREEMPT_RT, rw_semaphore and rwlock_t locks are unfair to writers.
+Readers can indefinitely acquire the lock unless the writer fully acquired
+the lock, which might never happen if there is always a reader in the
+critical section owning the lock.
+
+Mel Gorman reported that since LTP-20220121 the dio_truncate test case
+went from having 1 reader to having 16 readers and that number of readers
+is sufficient to prevent the down_write ever succeeding while readers
+exist. Eventually the test is killed after 30 minutes as a failure.
+
+Mel proposed a timeout to limit how long a writer can be blocked until
+the reader is forced into the slowpath.
+
+Thomas argued that there is no added value by providing this timeout.  From
+a PREEMPT_RT point of view, there are no critical rw_semaphore or rwlock_t
+locks left where the reader must be preferred.
+
+Mitigate indefinite writer starvation by forcing the READER into the
+slowpath once the WRITER attempts to acquire the lock.
+
+Reported-by: Mel Gorman <mgorman@techsingularity.net>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Signed-off-by: Ingo Molnar <mingo@kernel.org>
+Acked-by: Mel Gorman <mgorman@techsingularity.net>
+Link: https://lore.kernel.org/877cwbq4cq.ffs@tglx
+Link: https://lore.kernel.org/r/20230321161140.HMcQEhHb@linutronix.de
+Cc: Linus Torvalds <torvalds@linux-foundation.org>
+(cherry picked from commit 286deb7ec03d941664ac3ffaff58814b454adf65)
+Signed-off-by: Clark Williams <clark.williams@gmail.com>
+---
+ kernel/locking/rwbase_rt.c | 9 ---------
+ 1 file changed, 9 deletions(-)
+
+diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c
+index c201aadb9301..25ec0239477c 100644
+--- a/kernel/locking/rwbase_rt.c
++++ b/kernel/locking/rwbase_rt.c
+@@ -72,15 +72,6 @@ static int __sched __rwbase_read_lock(struct rwbase_rt *rwb,
+ 	int ret;
+ 
+ 	raw_spin_lock_irq(&rtm->wait_lock);
+-	/*
+-	 * Allow readers, as long as the writer has not completely
+-	 * acquired the semaphore for write.
+-	 */
+-	if (atomic_read(&rwb->readers) != WRITER_BIAS) {
+-		atomic_inc(&rwb->readers);
+-		raw_spin_unlock_irq(&rtm->wait_lock);
+-		return 0;
+-	}
+ 
+ 	/*
+ 	 * Call into the slow lock path with the rtmutex->wait_lock
+-- 
+2.43.0
+