diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2024-10-22 01:09:39 +0300 |
|---|---|---|
| committer | Uladzislau Rezki (Sony) <urezki@gmail.com> | 2024-12-14 19:13:09 +0300 |
| commit | d465492a224b2409508224cf6970d7b97e2285cc (patch) | |
| tree | 53df4c12beac3e066bc06cc57c8be9367056f5bd | |
| parent | fac04efc5c793dccbd07e2d59af9f90b7fc0dca4 (diff) | |
| download | linux-d465492a224b2409508224cf6970d7b97e2285cc.tar.xz | |
srcu: Guarantee non-negative return value from srcu_read_lock()
For almost 20 years, the int return value from srcu_read_lock() has
been always either zero or one. This commit therefore documents the
fact that it will be non-negative, and does the same for the underlying
__srcu_read_lock().
[ paulmck: Apply Andrii Nakryiko feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
| -rw-r--r-- | include/linux/srcu.h | 15 | ||||
| -rw-r--r-- | kernel/rcu/srcutree.c | 3 |
2 files changed, 10 insertions, 8 deletions
diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 08339eb8a01c..abaddd7e6ddf 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -232,13 +232,14 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp) * a mutex that is held elsewhere while calling synchronize_srcu() or * synchronize_srcu_expedited(). * - * The return value from srcu_read_lock() must be passed unaltered - * to the matching srcu_read_unlock(). Note that srcu_read_lock() and - * the matching srcu_read_unlock() must occur in the same context, for - * example, it is illegal to invoke srcu_read_unlock() in an irq handler - * if the matching srcu_read_lock() was invoked in process context. Or, - * for that matter to invoke srcu_read_unlock() from one task and the - * matching srcu_read_lock() from another. + * The return value from srcu_read_lock() is guaranteed to be + * non-negative. This value must be passed unaltered to the matching + * srcu_read_unlock(). Note that srcu_read_lock() and the matching + * srcu_read_unlock() must occur in the same context, for example, it is + * illegal to invoke srcu_read_unlock() in an irq handler if the matching + * srcu_read_lock() was invoked in process context. Or, for that matter to + * invoke srcu_read_unlock() from one task and the matching srcu_read_lock() + * from another. */ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) { diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 5e2e53464794..26ef58b481aa 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -738,7 +738,8 @@ EXPORT_SYMBOL_GPL(__srcu_check_read_flavor); /* * Counts the new reader in the appropriate per-CPU element of the * srcu_struct. - * Returns an index that must be passed to the matching srcu_read_unlock(). + * Returns a guaranteed non-negative index that must be passed to the + * matching __srcu_read_unlock(). */ int __srcu_read_lock(struct srcu_struct *ssp) { |