korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-12-02 00:24:12 +08:00
Code Issues Packages Projects Releases Wiki Activity

rcu: Remove leg of force_quiescent_state() switch statement

Browse Source 
The comparisons of rsp->gpnum nad rsp->completed in
rcu_process_dyntick() and force_quiescent_state() can be
replaced by the much more clear rcu_gp_in_progress() predicate
function.  After doing this, it becomes clear that the
RCU_SAVE_COMPLETED leg of the force_quiescent_state() function's
switch statement is almost completely a no-op.  A small change
to the RCU_SAVE_DYNTICK leg renders it a complete no-op, after
which it can be removed.  Doing so also eliminates the forcenow
local variable from force_quiescent_state().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <12626465501781-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul E. McKenney 2010-01-04 15:09:07 -08:00 committed by Ingo Molnar
parent 0f10dc8266
commit ee47eb9f4d
2 changed files with 7 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
kernel/rcutree.c
View File

@ -1144,6 +1144,7 @@ void rcu_check_callbacks(int cpu, int user)
/*
* Scan the leaf rcu_node structures, processing dyntick state for any that
* have not yet encountered a quiescent state, using the function specified.
* The caller must have suppressed start of new grace periods.
*/
static void rcu_process_dyntick(struct rcu_state *rsp,
int (*f)(struct rcu_data *))
@ -1157,7 +1158,7 @@ static void rcu_process_dyntick(struct rcu_state *rsp,
rcu_for_each_leaf_node(rsp, rnp) {
mask = 0;
spin_lock_irqsave(&rnp->lock, flags);
if (rnp->completed != rsp->gpnum - 1) {
if (!rcu_gp_in_progress(rsp)) {
spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
@ -1171,7 +1172,7 @@ static void rcu_process_dyntick(struct rcu_state *rsp,
if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))
mask |= bit;
}
if (mask != 0 && rnp->completed == rsp->gpnum - 1) {
if (mask != 0 && rcu_gp_in_progress(rsp)) {
/* rcu_report_qs_rnp() releases rnp->lock. */
rcu_report_qs_rnp(mask, rsp, rnp, flags);
@ -1189,7 +1190,6 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
{
unsigned long flags;
struct rcu_node *rnp = rcu_get_root(rsp);
u8 forcenow;
if (!rcu_gp_in_progress(rsp))
return; /* No grace period in progress, nothing to force. */
@ -1224,21 +1224,9 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
/* Record dyntick-idle state. */
rcu_process_dyntick(rsp, dyntick_save_progress_counter);
spin_lock(&rnp->lock); /* irqs already disabled */
if (!rcu_gp_in_progress(rsp))
break;
/* fall into next case. */
case RCU_SAVE_COMPLETED:
/* Update state, record completion counter. */
forcenow = 0;
if (rsp->gpnum - 1 == rsp->completed) {
forcenow = rsp->signaled == RCU_SAVE_COMPLETED;
if (rcu_gp_in_progress(rsp))
rsp->signaled = RCU_FORCE_QS;
}
if (!forcenow)
break;
/* fall into next case. */
break;
case RCU_FORCE_QS:

5
kernel/rcutree.h
View File

@ -237,12 +237,11 @@ struct rcu_data {
#define RCU_GP_IDLE 0 /* No grace period in progress. */
#define RCU_GP_INIT 1 /* Grace period being initialized. */
#define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */
#define RCU_SAVE_COMPLETED 3 /* Need to save rsp->completed. */
#define RCU_FORCE_QS 4 /* Need to force quiescent state. */
#define RCU_FORCE_QS 3 /* Need to force quiescent state. */
#ifdef CONFIG_NO_HZ
#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
#else /* #ifdef CONFIG_NO_HZ */
#define RCU_SIGNAL_INIT RCU_SAVE_COMPLETED
#define RCU_SIGNAL_INIT RCU_FORCE_QS
#endif /* #else #ifdef CONFIG_NO_HZ */
#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */