@@ -63,7 +63,9 @@ struct zram_table_entry {
unsigned long element;
};
unsigned long flags;
+#ifdef CONFIG_PREEMPT_RT
spinlock_t lock;
+#endif
#ifdef CONFIG_ZRAM_MEMORY_TRACKING
ktime_t ac_time;
#endif
@@ -2564,9 +2564,11 @@ EXPORT_SYMBOL(d_rehash);
static inline unsigned start_dir_add(struct inode *dir)
{
/*
- * The caller has a spinlock_t (dentry::d_lock) acquired which disables
- * preemption on !PREEMPT_RT. On PREEMPT_RT the lock does not disable
- * preemption and it has be done explicitly.
+ * 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();
@@ -2709,11 +2711,19 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
}
EXPORT_SYMBOL(d_alloc_parallel);
-static wait_queue_head_t *__d_lookup_clear_d_wait(struct dentry *dentry)
+/*
+ * - Unhash the dentry
+ * - Retrieve and clear the waitqueue head in dentry
+ * - Return the waitqueue head
+ */
+static wait_queue_head_t *__d_lookup_unhash(struct dentry *dentry)
{
wait_queue_head_t *d_wait;
- struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent,
- dentry->d_name.hash);
+ struct hlist_bl_head *b;
+
+ lockdep_assert_held(&dentry->d_lock);
+
+ b = in_lookup_hash(dentry->d_parent, dentry->d_name.hash);
hlist_bl_lock(b);
dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
__hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
@@ -2727,12 +2737,9 @@ static wait_queue_head_t *__d_lookup_clear_d_wait(struct dentry *dentry)
void __d_lookup_done(struct dentry *dentry)
{
- wait_queue_head_t *wq_head;
-
spin_lock(&dentry->d_lock);
- wq_head = __d_lookup_clear_d_wait(dentry);
+ wake_up_all(__d_lookup_unhash(dentry));
spin_unlock(&dentry->d_lock);
- wake_up_all(wq_head);
}
EXPORT_SYMBOL(__d_lookup_done);
@@ -2740,15 +2747,15 @@ EXPORT_SYMBOL(__d_lookup_done);
static inline void __d_add(struct dentry *dentry, struct inode *inode)
{
- wait_queue_head_t *d_wait = NULL;
+ wait_queue_head_t *d_wait;
struct inode *dir = NULL;
-
unsigned n;
+
spin_lock(&dentry->d_lock);
if (unlikely(d_in_lookup(dentry))) {
dir = dentry->d_parent->d_inode;
n = start_dir_add(dir);
- d_wait = __d_lookup_clear_d_wait(dentry);
+ d_wait = __d_lookup_unhash(dentry);
}
if (inode) {
unsigned add_flags = d_flags_for_inode(inode);
@@ -2759,11 +2766,11 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
fsnotify_update_flags(dentry);
}
__d_rehash(dentry);
- if (dir)
+ if (dir) {
end_dir_add(dir, n);
- spin_unlock(&dentry->d_lock);
- if (d_wait)
wake_up_all(d_wait);
+ }
+ spin_unlock(&dentry->d_lock);
if (inode)
spin_unlock(&inode->i_lock);
}
@@ -2908,8 +2915,8 @@ static void copy_name(struct dentry *dentry, struct dentry *target)
static void __d_move(struct dentry *dentry, struct dentry *target,
bool exchange)
{
- wait_queue_head_t *d_wait = NULL;
struct dentry *old_parent, *p;
+ wait_queue_head_t *d_wait;
struct inode *dir = NULL;
unsigned n;
@@ -2940,7 +2947,7 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
if (unlikely(d_in_lookup(target))) {
dir = target->d_parent->d_inode;
n = start_dir_add(dir);
- d_wait = __d_lookup_clear_d_wait(target);
+ d_wait = __d_lookup_unhash(target);
}
write_seqcount_begin(&dentry->d_seq);
@@ -2975,8 +2982,10 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
write_seqcount_end(&target->d_seq);
write_seqcount_end(&dentry->d_seq);
- if (dir)
+ if (dir) {
end_dir_add(dir, n);
+ wake_up_all(d_wait);
+ }
if (dentry->d_parent != old_parent)
spin_unlock(&dentry->d_parent->d_lock);
@@ -2984,8 +2993,6 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
spin_unlock(&old_parent->d_lock);
spin_unlock(&target->d_lock);
spin_unlock(&dentry->d_lock);
- if (d_wait)
- wake_up_all(d_wait);
}
/*
@@ -1 +1 @@
--rt2
+-rt3
Dear RT folks! I'm pleased to announce the v5.19-rc2-rt3 patch set. Changes since v5.19-rc2-rt2: - Don't a spinlock_t in the zram driver on non-PREEMPT_RT builds. - Redo the dcache patch and move the wake-up back under the dentry::lock lock protection to avoid problems on spurious wake-ups. Known issues - Valentin Schneider reported a few splats on ARM64, see https://lkml.kernel.org/r/20210810134127.1394269-1-valentin.schneider@arm.com The delta patch against v5.19-rc2-rt2 is appended below and can be found here: https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.19/incr/patch-5.19-rc2-rt2-rt3.patch.xz You can get this release via the git tree at: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v5.19-rc2-rt3 The RT patch against v5.19-rc2 can be found here: https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.19/older/patch-5.19-rc2-rt3.patch.xz The split quilt queue is available at: https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.19/older/patches-5.19-rc2-rt3.tar.xz Sebastian