Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 3842a083 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Document same-context read-side constraints 



The intent is that a given RCU read-side critical section be confined
to a single context.  For example, it is illegal to invoke rcu_read_lock()
in an exception handler and then invoke rcu_read_unlock() from the
context of the task that received the exception.

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent f0e7c19d

include/linux/rcupdate.h

+15 −0
Original line number Diff line number Diff line
@@ -265,6 +265,11 @@ extern int debug_lockdep_rcu_enabled(void); 
 *

 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot

 * and while lockdep is disabled.

 *

 * Note that rcu_read_lock() and the matching rcu_read_unlock() must

 * occur in the same context, for example, it is illegal to invoke

 * rcu_read_unlock() in process context if the matching rcu_read_lock()

 * was invoked from within an irq handler.

 */

static inline int rcu_read_lock_held(void)

{
@@ -689,6 +694,11 @@ static inline void rcu_read_unlock(void) 
 * critical sections in interrupt context can use just rcu_read_lock(),

 * though this should at least be commented to avoid confusing people

 * reading the code.

 *

 * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh()

 * must occur in the same context, for example, it is illegal to invoke

 * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh()

 * was invoked from some other task.

 */

static inline void rcu_read_lock_bh(void)

{
@@ -716,6 +726,11 @@ static inline void rcu_read_unlock_bh(void) 
 * are being done using call_rcu_sched() or synchronize_rcu_sched().

 * Read-side critical sections can also be introduced by anything that

 * disables preemption, including local_irq_disable() and friends.

 *

 * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched()

 * must occur in the same context, for example, it is illegal to invoke

 * rcu_read_unlock_sched() from process context if the matching

 * rcu_read_lock_sched() was invoked from an NMI handler.

 */

static inline void rcu_read_lock_sched(void)

{

include/linux/srcu.h

+5 −0
Original line number Diff line number Diff line
@@ -158,6 +158,11 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp) 
 * one way to indirectly wait on an SRCU grace period is to acquire

 * a mutex that is held elsewhere while calling synchronize_srcu() or

 * synchronize_srcu_expedited().

 *

 * 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.

 */

static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)

{