diff options
Diffstat (limited to 'debian/patches-rt/0002-fs-dcache-Disable-preemption-on-i_dir_seq-write-side.patch')
| -rw-r--r-- | debian/patches-rt/0002-fs-dcache-Disable-preemption-on-i_dir_seq-write-side.patch | 61 |
1 files changed, 0 insertions, 61 deletions
diff --git a/debian/patches-rt/0002-fs-dcache-Disable-preemption-on-i_dir_seq-write-side.patch b/debian/patches-rt/0002-fs-dcache-Disable-preemption-on-i_dir_seq-write-side.patch deleted file mode 100644 index 30a147af3..000000000 --- a/debian/patches-rt/0002-fs-dcache-Disable-preemption-on-i_dir_seq-write-side.patch +++ /dev/null @@ -1,61 +0,0 @@ -From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> -Date: Sun, 12 Jun 2022 16:27:28 +0200 -Subject: [PATCH 2/4] fs/dcache: Disable preemption on i_dir_seq write side on - PREEMPT_RT -Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.19/older/patches-5.19-rc8-rt9.tar.xz - -i_dir_seq is a sequence counter with a lock which is represented by the -lowest bit. The writer atomically updates the counter which ensures that it -can be modified by only one writer at a time. This requires preemption to -be disabled across the write side critical section. - -On !PREEMPT_RT kernels this is implicit by the caller acquiring -dentry::lock. On PREEMPT_RT kernels spin_lock() does not disable preemption -which means that a preempting writer or reader would live lock. It's -therefore required to disable preemption explicitly. - -An alternative solution would be to replace i_dir_seq with a seqlock_t for -PREEMPT_RT, but that comes with its own set of problems due to arbitrary -lock nesting. A pure sequence count with an associated spinlock is not -possible because the locks held by the caller are not necessarily related. - -As the critical section is small, disabling preemption is a sensible -solution. - -Reported-by: Oleg.Karfich@wago.com -Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> -Signed-off-by: Thomas Gleixner <tglx@linutronix.de> -Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> -Link: https://lkml.kernel.org/r/20220613140712.77932-2-bigeasy@linutronix.de ---- - fs/dcache.c | 12 +++++++++++- - 1 file changed, 11 insertions(+), 1 deletion(-) - ---- a/fs/dcache.c -+++ b/fs/dcache.c -@@ -2564,7 +2564,15 @@ EXPORT_SYMBOL(d_rehash); - - static inline unsigned start_dir_add(struct inode *dir) - { -- -+ /* -+ * The caller holds a spinlock (dentry::d_lock). On !PREEMPT_RT -+ * kernels spin_lock() implicitly disables preemption, but not on -+ * PREEMPT_RT. So for RT it has to be done explicitly to protect -+ * the sequence count write side critical section against a reader -+ * or another writer preempting, which would result in a live lock. -+ */ -+ if (IS_ENABLED(CONFIG_PREEMPT_RT)) -+ preempt_disable(); - for (;;) { - unsigned n = dir->i_dir_seq; - if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n) -@@ -2576,6 +2584,8 @@ static inline unsigned start_dir_add(str - static inline void end_dir_add(struct inode *dir, unsigned n) - { - smp_store_release(&dir->i_dir_seq, n + 2); -+ if (IS_ENABLED(CONFIG_PREEMPT_RT)) -+ preempt_enable(); - } - - static void d_wait_lookup(struct dentry *dentry) |