seqlock: seqcount latch APIs: Only allow seqcount_latch_t

All latch sequence counter call-sites have now been converted from plain
seqcount_t to the new seqcount_latch_t data type.

Enforce type-safety by modifying seqlock.h latch APIs to only accept
seqcount_latch_t.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200827114044.11173-9-a.darwish@linutronix.de

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 88b917d4ebde692b3370d73af32d63d90c4acbee..f2a7a467e998a1b72c922dc3ca311c0ff49e39dc 100644 (file)
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -620,7 +620,7 @@ static inline void seqcount_latch_init(seqcount_latch_t *s)
 
 /**
  * raw_read_seqcount_latch() - pick even/odd latch data copy
- * @s: Pointer to seqcount_t, seqcount_raw_spinlock_t, or seqcount_latch_t
+ * @s: Pointer to seqcount_latch_t
  *
  * See raw_write_seqcount_latch() for details and a full reader/writer
  * usage example.
@@ -629,17 +629,14 @@ static inline void seqcount_latch_init(seqcount_latch_t *s)
  * picking which data copy to read. The full counter must then be checked
  * with read_seqcount_latch_retry().
  */
-#define raw_read_seqcount_latch(s)                                             \
-({                                                                             \
-       /*                                                                      \
-        * Pairs with the first smp_wmb() in raw_write_seqcount_latch().        \
-        * Due to the dependent load, a full smp_rmb() is not needed.           \
-        */                                                                     \
-       _Generic(*(s),                                                          \
-                seqcount_t:              READ_ONCE(((seqcount_t *)s)->sequence),                       \
-                seqcount_raw_spinlock_t: READ_ONCE(((seqcount_raw_spinlock_t *)s)->seqcount.sequence), \
-                seqcount_latch_t:        READ_ONCE(((seqcount_latch_t *)s)->seqcount.sequence));       \
-})
+static inline unsigned raw_read_seqcount_latch(const seqcount_latch_t *s)
+{
+       /*
+        * Pairs with the first smp_wmb() in raw_write_seqcount_latch().
+        * Due to the dependent load, a full smp_rmb() is not needed.
+        */
+       return READ_ONCE(s->seqcount.sequence);
+}
 
 /**
  * read_seqcount_latch_retry() - end a seqcount_latch_t read section
@@ -656,7 +653,7 @@ read_seqcount_latch_retry(const seqcount_latch_t *s, unsigned start)
 
 /**
  * raw_write_seqcount_latch() - redirect latch readers to even/odd copy
- * @s: Pointer to seqcount_t, seqcount_raw_spinlock_t, or seqcount_latch_t
+ * @s: Pointer to seqcount_latch_t
  *
  * The latch technique is a multiversion concurrency control method that allows
  * queries during non-atomic modifications. If you can guarantee queries never
@@ -735,14 +732,11 @@ read_seqcount_latch_retry(const seqcount_latch_t *s, unsigned start)
  *     When data is a dynamic data structure; one should use regular RCU
  *     patterns to manage the lifetimes of the objects within.
  */
-#define raw_write_seqcount_latch(s)                                            \
-{                                                                              \
-       smp_wmb();      /* prior stores before incrementing "sequence" */       \
-       _Generic(*(s),                                                          \
-               seqcount_t:             ((seqcount_t *)s)->sequence++,          \
-               seqcount_raw_spinlock_t:((seqcount_raw_spinlock_t *)s)->seqcount.sequence++, \
-               seqcount_latch_t:       ((seqcount_latch_t *)s)->seqcount.sequence++); \
-       smp_wmb();      /* increment "sequence" before following stores */      \
+static inline void raw_write_seqcount_latch(seqcount_latch_t *s)
+{
+       smp_wmb();      /* prior stores before incrementing "sequence" */
+       s->seqcount.sequence++;
+       smp_wmb();      /* increment "sequence" before following stores */
 }
 
 /*