seqlock, treewide: Switch to non-raw seqcount_latch interface

Switch all instrumentable users of the seqcount_latch interface over to
the non-raw interface.

Co-developed-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241104161910.780003-5-elver@google.com

arch/x86/kernel/tsc.c

@@ -174,10 +174,11 @@ static void __set_cyc2ns_scale(unsigned long khz, int cpu, unsigned long long ts
 
 	c2n = per_cpu_ptr(&cyc2ns, cpu);
 
-	raw_write_seqcount_latch(&c2n->seq);
+	write_seqcount_latch_begin(&c2n->seq);
 	c2n->data[0] = data;
-	raw_write_seqcount_latch(&c2n->seq);
+	write_seqcount_latch(&c2n->seq);
 	c2n->data[1] = data;
+	write_seqcount_latch_end(&c2n->seq);
 }
 
 static void set_cyc2ns_scale(unsigned long khz, int cpu, unsigned long long tsc_now)

include/linux/rbtree_latch.h

@@ -14,7 +14,7 @@
  *
  * If we need to allow unconditional lookups (say as required for NMI context
  * usage) we need a more complex setup; this data structure provides this by
- * employing the latch technique -- see @raw_write_seqcount_latch -- to
+ * employing the latch technique -- see @write_seqcount_latch_begin -- to
  * implement a latched RB-tree which does allow for unconditional lookups by
  * virtue of always having (at least) one stable copy of the tree.
  *
@@ -132,7 +132,7 @@ __lt_find(void *key, struct latch_tree_root *ltr, int idx,
  * @ops: operators defining the node order
  *
  * It inserts @node into @root in an ordered fashion such that we can always
- * observe one complete tree. See the comment for raw_write_seqcount_latch().
+ * observe one complete tree. See the comment for write_seqcount_latch_begin().
  *
  * The inserts use rcu_assign_pointer() to publish the element such that the
  * tree structure is stored before we can observe the new @node.
@@ -145,10 +145,11 @@ latch_tree_insert(struct latch_tree_node *node,
 		  struct latch_tree_root *root,
 		  const struct latch_tree_ops *ops)
 {
-	raw_write_seqcount_latch(&root->seq);
+	write_seqcount_latch_begin(&root->seq);
 	__lt_insert(node, root, 0, ops->less);
-	raw_write_seqcount_latch(&root->seq);
+	write_seqcount_latch(&root->seq);
 	__lt_insert(node, root, 1, ops->less);
+	write_seqcount_latch_end(&root->seq);
 }
 
 /**
@@ -159,7 +160,7 @@ latch_tree_insert(struct latch_tree_node *node,
  *
  * Removes @node from the trees @root in an ordered fashion such that we can
  * always observe one complete tree. See the comment for
- * raw_write_seqcount_latch().
+ * write_seqcount_latch_begin().
  *
  * It is assumed that @node will observe one RCU quiescent state before being
  * reused of freed.
@@ -172,10 +173,11 @@ latch_tree_erase(struct latch_tree_node *node,
 		 struct latch_tree_root *root,
 		 const struct latch_tree_ops *ops)
 {
-	raw_write_seqcount_latch(&root->seq);
+	write_seqcount_latch_begin(&root->seq);
 	__lt_erase(node, root, 0);
-	raw_write_seqcount_latch(&root->seq);
+	write_seqcount_latch(&root->seq);
 	__lt_erase(node, root, 1);
+	write_seqcount_latch_end(&root->seq);
 }
 
 /**
@@ -204,9 +206,9 @@ latch_tree_find(void *key, struct latch_tree_root *root,
 	unsigned int seq;
 
 	do {
-		seq = raw_read_seqcount_latch(&root->seq);
+		seq = read_seqcount_latch(&root->seq);
 		node = __lt_find(key, root, seq & 1, ops->comp);
-	} while (raw_read_seqcount_latch_retry(&root->seq, seq));
+	} while (read_seqcount_latch_retry(&root->seq, seq));
 
 	return node;
 }

kernel/printk/printk.c

@@ -560,10 +560,11 @@ bool printk_percpu_data_ready(void)
 /* Must be called under syslog_lock. */
 static void latched_seq_write(struct latched_seq *ls, u64 val)
 {
-	raw_write_seqcount_latch(&ls->latch);
+	write_seqcount_latch_begin(&ls->latch);
 	ls->val[0] = val;
-	raw_write_seqcount_latch(&ls->latch);
+	write_seqcount_latch(&ls->latch);
 	ls->val[1] = val;
+	write_seqcount_latch_end(&ls->latch);
 }
 
 /* Can be called from any context. */
@@ -574,10 +575,10 @@ static u64 latched_seq_read_nolock(struct latched_seq *ls)
 	u64 val;
 
 	do {
-		seq = raw_read_seqcount_latch(&ls->latch);
+		seq = read_seqcount_latch(&ls->latch);
 		idx = seq & 0x1;
 		val = ls->val[idx];
-	} while (raw_read_seqcount_latch_retry(&ls->latch, seq));
+	} while (read_seqcount_latch_retry(&ls->latch, seq));
 
 	return val;
 }

kernel/time/sched_clock.c

@@ -71,13 +71,13 @@ static __always_inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
 
 notrace struct clock_read_data *sched_clock_read_begin(unsigned int *seq)
 {
-	*seq = raw_read_seqcount_latch(&cd.seq);
+	*seq = read_seqcount_latch(&cd.seq);
 	return cd.read_data + (*seq & 1);
 }
 
 notrace int sched_clock_read_retry(unsigned int seq)
 {
-	return raw_read_seqcount_latch_retry(&cd.seq, seq);
+	return read_seqcount_latch_retry(&cd.seq, seq);
 }
 
 static __always_inline unsigned long long __sched_clock(void)
@@ -132,16 +132,18 @@ unsigned long long notrace sched_clock(void)
 static void update_clock_read_data(struct clock_read_data *rd)
 {
 	/* steer readers towards the odd copy */
-	raw_write_seqcount_latch(&cd.seq);
+	write_seqcount_latch_begin(&cd.seq);
 
 	/* now its safe for us to update the normal (even) copy */
 	cd.read_data[0] = *rd;
 
 	/* switch readers back to the even copy */
-	raw_write_seqcount_latch(&cd.seq);
+	write_seqcount_latch(&cd.seq);
 
 	/* update the backup (odd) copy with the new data */
 	cd.read_data[1] = *rd;
+
+	write_seqcount_latch_end(&cd.seq);
 }
 
 /*
@@ -279,7 +281,7 @@ void __init generic_sched_clock_init(void)
  */
 static u64 notrace suspended_sched_clock_read(void)
 {
-	unsigned int seq = raw_read_seqcount_latch(&cd.seq);
+	unsigned int seq = read_seqcount_latch(&cd.seq);
 
 	return cd.read_data[seq & 1].epoch_cyc;
 }

kernel/time/timekeeping.c

@@ -411,7 +411,7 @@ static inline u64 timekeeping_get_ns(const struct tk_read_base *tkr)
  * We want to use this from any context including NMI and tracing /
  * instrumenting the timekeeping code itself.
  *
- * Employ the latch technique; see @raw_write_seqcount_latch.
+ * Employ the latch technique; see @write_seqcount_latch.
  *
  * So if a NMI hits the update of base[0] then it will use base[1]
  * which is still consistent. In the worst case this can result is a
@@ -424,16 +424,18 @@ static void update_fast_timekeeper(const struct tk_read_base *tkr,
 	struct tk_read_base *base = tkf->base;
 
 	/* Force readers off to base[1] */
-	raw_write_seqcount_latch(&tkf->seq);
+	write_seqcount_latch_begin(&tkf->seq);
 
 	/* Update base[0] */
 	memcpy(base, tkr, sizeof(*base));
 
 	/* Force readers back to base[0] */
-	raw_write_seqcount_latch(&tkf->seq);
+	write_seqcount_latch(&tkf->seq);
 
 	/* Update base[1] */
 	memcpy(base + 1, base, sizeof(*base));
+
+	write_seqcount_latch_end(&tkf->seq);
 }
 
 static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
@@ -443,11 +445,11 @@ static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
 	u64 now;
 
 	do {
-		seq = raw_read_seqcount_latch(&tkf->seq);
+		seq = read_seqcount_latch(&tkf->seq);
 		tkr = tkf->base + (seq & 0x01);
 		now = ktime_to_ns(tkr->base);
 		now += __timekeeping_get_ns(tkr);
-	} while (raw_read_seqcount_latch_retry(&tkf->seq, seq));
+	} while (read_seqcount_latch_retry(&tkf->seq, seq));
 
 	return now;
 }