Commit Graph

7 Commits

Author SHA1 Message Date
Paul E. McKenney 7d0ae8086b rcu: Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE()
This commit moves from the old ACCESS_ONCE() API to the new READ_ONCE()
and WRITE_ONCE() APIs.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck:  Updated to include kernel/torture.c as suggested by Jason Low. ]
2015-05-27 12:56:15 -07:00
Paul E. McKenney 78e691f4ae Merge branches 'doc.2015.01.07a', 'fixes.2015.01.15a', 'preempt.2015.01.06a', 'srcu.2015.01.06a', 'stall.2015.01.16a' and 'torture.2015.01.11a' into HEAD
doc.2015.01.07a: Documentation updates.
fixes.2015.01.15a: Miscellaneous fixes.
preempt.2015.01.06a: Changes to handling of lists of preempted tasks.
srcu.2015.01.06a: SRCU updates.
stall.2015.01.16a: RCU CPU stall-warning updates and fixes.
torture.2015.01.11a: RCU torture-test updates and fixes.
2015-01-15 23:34:34 -08:00
Miroslav Benes ec1fe396ff rcu: Fix RCU CPU stall detection in tiny implementation
The tiny RCU CPU stall detection depends on *rcp->curtail not being
NULL. It is however a tail pointer and thus NULL by definition. Instead we
should check rcp->rcucblist for the presence of pending callbacks which
need to be processed. With this fix INFO about the stall is printed and
jiffies_stall (jiffies at next stall) correctly updated.

Note that the check for pending callback is necessary to avoid spurious
warnings if there are no pendings callbacks.

Signed-off-by: Miroslav Benes <mbenes@suse.cz>
[ paulmck: Fused identical "if" statements, ported to -rcu. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-01-15 23:33:16 -08:00
Lai Jiangshan 5f6130fa52 tiny_rcu: Directly force QS when call_rcu_[bh|sched]() on idle_task
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>
2015-01-06 11:01:12 -08:00
Himangi Saraogi af952b919b rcu: Protect uses of ->jiffies_stall with ACCESS_ONCE()
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>
2014-04-29 08:44:41 -07:00
Paul E. McKenney 87de1cfdc5 rcu: Stop tracking FSF's postal address
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>
2014-02-17 15:01:37 -08:00
Paul E. McKenney 4102adab91 rcu: Move RCU-related source code to kernel/rcu directory
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
2013-10-15 12:53:31 -07:00