/**
* rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section
*
- * This is equivalent of rcu_read_lock(), but to be used when updates
- * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since
- * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a
- * softirq handler to be a quiescent state, a process in RCU read-side
- * critical section must be protected by disabling softirqs. Read-side
- * 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.
+ * This is equivalent of rcu_read_lock(), but also disables softirqs.
+ * Note that synchronize_rcu() and friends may be used for the update
+ * side, although synchronize_rcu_bh() is available as a wrapper in the
+ * short term. Longer term, the _bh update-side API will be eliminated.
*
* 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
* @...: List of call_rcu() functions for the flavors to wait on.
*
* This macro waits concurrently for multiple flavors of RCU grace periods.
- * For example, synchronize_rcu_mult(call_rcu, call_rcu_bh) would wait
- * on concurrent RCU and RCU-bh grace periods. Waiting on a give SRCU
+ * For example, synchronize_rcu_mult(call_rcu, call_rcu_sched) would wait
+ * on concurrent RCU and RCU-sched grace periods. Waiting on a give SRCU
* domain requires you to write a wrapper function for that SRCU domain's
* call_srcu() function, supplying the corresponding srcu_struct.
*
* If Tiny RCU, tell _wait_rcu_gp() not to bother waiting for RCU
- * or RCU-bh, given that anywhere synchronize_rcu_mult() can be called
+ * or RCU-sched, given that anywhere synchronize_rcu_mult() can be called
* is automatically a grace period.
*/
#define synchronize_rcu_mult(...) \
/**
* synchronize_rcu_bh_expedited - Brute-force RCU-bh grace period
*
- * Wait for an RCU-bh grace period to elapse, but use a "big hammer"
- * approach to force the grace period to end quickly. This consumes
- * significant time on all CPUs and is unfriendly to real-time workloads,
- * so is thus not recommended for any sort of common-case code. In fact,
- * if you are using synchronize_rcu_bh_expedited() in a loop, please
- * restructure your code to batch your updates, and then use a single
- * synchronize_rcu_bh() instead.
- *
- * Note that it is illegal to call this function while holding any lock
- * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
- * to call this function from a CPU-hotplug notifier. Failing to observe
- * these restriction will result in deadlock.
+ * This is a transitional API and will soon be removed, with all
+ * callers converted to synchronize_rcu_expedited().
*/
static inline void synchronize_rcu_bh_expedited(void)
{
CPUs specified at boot time by the rcu_nocbs parameter.
For each such CPU, a kthread ("rcuox/N") will be created to
invoke callbacks, where the "N" is the CPU being offloaded,
- and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
- "s" for RCU-sched. Nothing prevents this kthread from running
- on the specified CPUs, but (1) the kthreads may be preempted
- between each callback, and (2) affinity or cgroups can be used
- to force the kthreads to run on whatever set of CPUs is desired.
+ and where the "p" for RCU-preempt and "s" for RCU-sched.
+ Nothing prevents this kthread from running on the specified
+ CPUs, but (1) the kthreads may be preempted between each
+ callback, and (2) affinity or cgroups can be used to force
+ the kthreads to run on whatever set of CPUs is desired.
Say Y here if you want to help to debug reduced OS jitter.
Say N here if you are unsure.
EXPORT_SYMBOL_GPL(rcu_sched_get_gp_seq);
/*
- * Return the number of RCU-bh GPs completed thus far for debug & stats.
+ * Return the number of RCU GPs completed thus far for debug & stats.
+ * This is a transitional API and will soon be removed.
*/
unsigned long rcu_bh_get_gp_seq(void)
{
EXPORT_SYMBOL_GPL(kfree_call_rcu);
/*
- * Because a context switch is a grace period for RCU-sched and RCU-bh,
- * any blocking grace-period wait automatically implies a grace period
- * if there is only one CPU online at any point time during execution
- * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to
- * occasionally incorrectly indicate that there are multiple CPUs online
- * when there was in fact only one the whole time, as this just adds
- * some overhead: RCU still operates correctly.
+ * Because a context switch is a grace period for RCU-sched, any blocking
+ * grace-period wait automatically implies a grace period if there
+ * is only one CPU online at any point time during execution of either
+ * synchronize_sched() or synchronize_rcu_bh(). It is OK to occasionally
+ * incorrectly indicate that there are multiple CPUs online when there
+ * was in fact only one the whole time, as this just adds some overhead:
+ * RCU still operates correctly.
*/
static int rcu_blocking_is_gp(void)
{
*
* Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
*
- * Note that rcu_read_lock() is disallowed if the CPU is either idle or
+ * Note that rcu_read_lock_bh() is disallowed if the CPU is either idle or
* offline from an RCU perspective, so check for those as well.
*/
int rcu_read_lock_bh_held(void)
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