For RCU in UP, context-switch = QS = GP, thus we can force a
context-switch when any call_rcu_[bh|sched]() is happened on idle_task.
After doing so, rcu_idle/irq_enter/exit() are useless, so we can simply
make these functions empty.
More important, this change does not change the functionality logically.
Note: raise_softirq(RCU_SOFTIRQ)/rcu_sched_qs() in rcu_idle_enter() and
outmost rcu_irq_exit() will have to wake up the ksoftirqd
(due to in_interrupt() == 0).
Before this patch After this patch:
call_rcu_sched() in idle; call_rcu_sched() in idle
set resched
do other stuffs; do other stuffs
outmost rcu_irq_exit() outmost rcu_irq_exit() (empty function)
(or rcu_idle_enter()) (or rcu_idle_enter(), also empty function)
start to resched. (see above)
rcu_sched_qs() rcu_sched_qs()
QS,and GP and advance cb QS,and GP and advance cb
wake up the ksoftirqd wake up the ksoftirqd
set resched
resched to ksoftirqd (or other) resched to ksoftirqd (or other)
These two code patches are almost the same.
Size changed after patched:
size kernel/rcu/tiny-old.o kernel/rcu/tiny-patched.o
text data bss dec hex filename
3449 206 8 3663 e4f kernel/rcu/tiny-old.o
2406 144 8 2558 9fe kernel/rcu/tiny-patched.o
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Some of the accesses to the rcu_state structure's ->jiffies_stall
field are unprotected. This patch protects them with ACCESS_ONCE().
The following coccinelle script was used to acheive this:
/* coccinelle script to protect uses of ->jiffies_stall with ACCESS_ONCE() */
@@
identifier a;
@@
(
ACCESS_ONCE(a->jiffies_stall)
|
- a->jiffies_stall
+ ACCESS_ONCE(a->jiffies_stall)
)
Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
All of the RCU source files have the usual GPL header, which contains a
long-obsolete postal address for FSF. To avoid the need to track the
FSF office's movements, this commit substitutes the URL where GPL may
be found.
Reported-by: Greg KH <gregkh@linuxfoundation.org>
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
