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rcu: Move expedited code from tree_plugin.h to tree_exp.h 

People have been having some difficulty finding their way around the
RCU code.  This commit therefore pulls some of the expedited grace-period
code from tree_plugin.h to a new tree_exp.h file.  This commit is strictly
code movement.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2016-04-15 16:44:07 -07:00
parent 3549c2bc2c
commit 40e0a6cfd5
2 changed files with 94 additions and 88 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

94
kernel/rcu/tree_exp.h
View File

@ -562,3 +562,97 @@ void synchronize_sched_expedited(void)
rcu_exp_wait_wake(rsp, s);
}
EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
#ifdef CONFIG_PREEMPT_RCU
/*
* Remote handler for smp_call_function_single(). If there is an
* RCU read-side critical section in effect, request that the
* next rcu_read_unlock() record the quiescent state up the
* ->expmask fields in the rcu_node tree. Otherwise, immediately
* report the quiescent state.
*/
static void sync_rcu_exp_handler(void *info)
{
struct rcu_data *rdp;
struct rcu_state *rsp = info;
struct task_struct *t = current;
/*
* Within an RCU read-side critical section, request that the next
* rcu_read_unlock() report. Unless this RCU read-side critical
* section has already blocked, in which case it is already set
* up for the expedited grace period to wait on it.
*/
if (t->rcu_read_lock_nesting > 0 &&
!t->rcu_read_unlock_special.b.blocked) {
t->rcu_read_unlock_special.b.exp_need_qs = true;
return;
}
/*
* We are either exiting an RCU read-side critical section (negative
* values of t->rcu_read_lock_nesting) or are not in one at all
* (zero value of t->rcu_read_lock_nesting). Or we are in an RCU
* read-side critical section that blocked before this expedited
* grace period started. Either way, we can immediately report
* the quiescent state.
*/
rdp = this_cpu_ptr(rsp->rda);
rcu_report_exp_rdp(rsp, rdp, true);
}
/**
* synchronize_rcu_expedited - Brute-force RCU grace period
*
* Wait for an RCU-preempt grace period, but expedite it. The basic
* idea is to IPI all non-idle non-nohz online CPUs. The IPI handler
* checks whether the CPU is in an RCU-preempt critical section, and
* if so, it sets a flag that causes the outermost rcu_read_unlock()
* to report the quiescent state. On the other hand, if the CPU is
* not in an RCU read-side critical section, the IPI handler reports
* the quiescent state immediately.
*
* Although this is a greate improvement over previous expedited
* implementations, it is still 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_expedited() in a loop, please restructure
* your code to batch your updates, and then Use a single synchronize_rcu()
* instead.
*/
void synchronize_rcu_expedited(void)
{
struct rcu_state *rsp = rcu_state_p;
unsigned long s;
/* If expedited grace periods are prohibited, fall back to normal. */
if (rcu_gp_is_normal()) {
wait_rcu_gp(call_rcu);
return;
}
s = rcu_exp_gp_seq_snap(rsp);
if (exp_funnel_lock(rsp, s))
return; /* Someone else did our work for us. */
/* Initialize the rcu_node tree in preparation for the wait. */
sync_rcu_exp_select_cpus(rsp, sync_rcu_exp_handler);
/* Wait for ->blkd_tasks lists to drain, then wake everyone up. */
rcu_exp_wait_wake(rsp, s);
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
#else /* #ifdef CONFIG_PREEMPT_RCU */
/*
* Wait for an rcu-preempt grace period, but make it happen quickly.
* But because preemptible RCU does not exist, map to rcu-sched.
*/
void synchronize_rcu_expedited(void)
{
synchronize_sched_expedited();
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */

88
kernel/rcu/tree_plugin.h
View File

@ -681,84 +681,6 @@ void synchronize_rcu(void)
}
EXPORT_SYMBOL_GPL(synchronize_rcu);
/*
* Remote handler for smp_call_function_single(). If there is an
* RCU read-side critical section in effect, request that the
* next rcu_read_unlock() record the quiescent state up the
* ->expmask fields in the rcu_node tree. Otherwise, immediately
* report the quiescent state.
*/
static void sync_rcu_exp_handler(void *info)
{
struct rcu_data *rdp;
struct rcu_state *rsp = info;
struct task_struct *t = current;
/*
* Within an RCU read-side critical section, request that the next
* rcu_read_unlock() report. Unless this RCU read-side critical
* section has already blocked, in which case it is already set
* up for the expedited grace period to wait on it.
*/
if (t->rcu_read_lock_nesting > 0 &&
!t->rcu_read_unlock_special.b.blocked) {
t->rcu_read_unlock_special.b.exp_need_qs = true;
return;
}
/*
* We are either exiting an RCU read-side critical section (negative
* values of t->rcu_read_lock_nesting) or are not in one at all
* (zero value of t->rcu_read_lock_nesting). Or we are in an RCU
* read-side critical section that blocked before this expedited
* grace period started. Either way, we can immediately report
* the quiescent state.
*/
rdp = this_cpu_ptr(rsp->rda);
rcu_report_exp_rdp(rsp, rdp, true);
}
/**
* synchronize_rcu_expedited - Brute-force RCU grace period
*
* Wait for an RCU-preempt grace period, but expedite it. The basic
* idea is to IPI all non-idle non-nohz online CPUs. The IPI handler
* checks whether the CPU is in an RCU-preempt critical section, and
* if so, it sets a flag that causes the outermost rcu_read_unlock()
* to report the quiescent state. On the other hand, if the CPU is
* not in an RCU read-side critical section, the IPI handler reports
* the quiescent state immediately.
*
* Although this is a greate improvement over previous expedited
* implementations, it is still 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_expedited() in a loop, please restructure
* your code to batch your updates, and then Use a single synchronize_rcu()
* instead.
*/
void synchronize_rcu_expedited(void)
{
struct rcu_state *rsp = rcu_state_p;
unsigned long s;
/* If expedited grace periods are prohibited, fall back to normal. */
if (rcu_gp_is_normal()) {
wait_rcu_gp(call_rcu);
return;
}
s = rcu_exp_gp_seq_snap(rsp);
if (exp_funnel_lock(rsp, s))
return; /* Someone else did our work for us. */
/* Initialize the rcu_node tree in preparation for the wait. */
sync_rcu_exp_select_cpus(rsp, sync_rcu_exp_handler);
/* Wait for ->blkd_tasks lists to drain, then wake everyone up. */
rcu_exp_wait_wake(rsp, s);
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
/**
* rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
*
@ -882,16 +804,6 @@ static void rcu_preempt_check_callbacks(void)
{
}
/*
* Wait for an rcu-preempt grace period, but make it happen quickly.
* But because preemptible RCU does not exist, map to rcu-sched.
*/
void synchronize_rcu_expedited(void)
{
synchronize_sched_expedited();
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
/*
* Because preemptible RCU does not exist, rcu_barrier() is just
* another name for rcu_barrier_sched().