srcu: Document that srcu_{read_lock,down_read}() can share srcu_struct

paulmckrcu · fbq · commit 729fb74889d9 · 2025-02-05T07:12:06.000-08:00
This commit adds a sentence to the srcu_down_read() function's kernel-doc
header noting that it is permissible to use srcu_down_read() and
srcu_read_lock() on the same srcu_struct, even concurrently.

Signed-off-by: Paul E. McKenney &lt;paulmck@kernel.org&gt;
Cc: Alexei Starovoitov &lt;ast@kernel.org&gt;
Cc: Andrii Nakryiko &lt;andrii@kernel.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
Cc: &lt;bpf@vger.kernel.org&gt;
Signed-off-by: Boqun Feng &lt;boqun.feng@gmail.com&gt;
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
@@ -359,7 +359,8 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
  * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler.
  *
  * Calls to srcu_down_read() may be nested, similar to the manner in
- * which calls to down_read() may be nested.
+ * which calls to down_read() may be nested.  The same srcu_struct may be
+ * used concurrently by srcu_down_read() and srcu_read_lock().
  */
 static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp)
 {

Original file line number	Diff line number	Diff line change
`@@ -359,7 +359,8 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)`
`359`	`359`	`* srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler.`
`360`	`360`	`*`
`361`	`361`	`* Calls to srcu_down_read() may be nested, similar to the manner in`
`362`		`- * which calls to down_read() may be nested.`
	`362`	`+ * which calls to down_read() may be nested. The same srcu_struct may be`
	`363`	`+ * used concurrently by srcu_down_read() and srcu_read_lock().`
`363`	`364`	`*/`
`364`	`365`	`static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp)`
`365`	`366`	`{`