Please pull the latest core-locking-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git core-locking-for-linus

Something screwed up? This was the core-locking pull request, not the RCU pull. And there's no shortlog or diff..

Linus

Ingo Molnar

author

2011-03-16 06:59 UTC #2 lore raw

Quoted 8 lines · Linus Torvalds

Quoted 4 lines · Ingo Molnar
Please pull the latest core-locking-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git core-locking-for-linus
Something screwed up? This was the core-locking pull request, not the RCU pull. And there's no shortlog or diff..

Oops, indeed. The right one is:

Please pull the latest core-rcu-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git core-rcu-for-linus

Thanks,

Ingo

------------------>
Amerigo Wang (1):
rcupdate: remove dead code

Jesper Juhl (1):
rcutorture: Get rid of duplicate sched.h include

Lai Jiangshan (1):
rcu: call __rcu_read_unlock() in exit_rcu for tiny RCU

Paul E. McKenney (3):
rcu: add documentation saying which RCU flavor to choose
rcu: add comment saying why DEBUG_OBJECTS_RCU_HEAD depends on PREEMPT.
smp: Document transitivity for memory barriers.

 Documentation/RCU/whatisRCU.txt   |   31 +++++++++++++++++++
 Documentation/memory-barriers.txt |   58 +++++++++++++++++++++++++++++++++++++
 kernel/rcupdate.c                 |   10 +++---
 kernel/rcutiny_plugin.h           |    2 +-
 kernel/rcutorture.c               |    1 -
 5 files changed, 95 insertions(+), 7 deletions(-)

Documentation/RCU/whatisRCU.txt +31 -0

index cfaac34..6ef6926 100644
@@ -849,6 +849,37 @@ All:  lockdep-checked RCU-protected pointer access
 See the comment headers in the source code (or the docbook generated
 from them) for more information.
 
+However, given that there are no fewer than four families of RCU APIs
+in the Linux kernel, how do you choose which one to use?  The following
+list can be helpful:
+
+a.	Will readers need to block?  If so, you need SRCU.
+
+b.	What about the -rt patchset?  If readers would need to block
+	in an non-rt kernel, you need SRCU.  If readers would block
+	in a -rt kernel, but not in a non-rt kernel, SRCU is not
+	necessary.
+
+c.	Do you need to treat NMI handlers, hardirq handlers,
+	and code segments with preemption disabled (whether
+	via preempt_disable(), local_irq_save(), local_bh_disable(),
+	or some other mechanism) as if they were explicit RCU readers?
+	If so, you need RCU-sched.
+
+d.	Do you need RCU grace periods to complete even in the face
+	of softirq monopolization of one or more of the CPUs?  For
+	example, is your code subject to network-based denial-of-service
+	attacks?  If so, you need RCU-bh.
+
+e.	Is your workload too update-intensive for normal use of
+	RCU, but inappropriate for other synchronization mechanisms?
+	If so, consider SLAB_DESTROY_BY_RCU.  But please be careful!
+
+f.	Otherwise, use RCU.
+
+Of course, this all assumes that you have determined that RCU is in fact
+the right tool for your job.
+
 
 8.  ANSWERS TO QUICK QUIZZES

Documentation/memory-barriers.txt +58 -0

70 lines not on this page · raw message

kernel/rcupdate.c +5 -5

index a23a57a..f3240e9 100644
@@ -214,11 +214,12 @@ static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
 		 * Ensure that queued callbacks are all executed.
 		 * If we detect that we are nested in a RCU read-side critical
 		 * section, we should simply fail, otherwise we would deadlock.
+		 * Note that the machinery to reliably determine whether
+		 * or not we are in an RCU read-side critical section
+		 * exists only in the preemptible RCU implementations
+		 * (TINY_PREEMPT_RCU and TREE_PREEMPT_RCU), which is why
+		 * DEBUG_OBJECTS_RCU_HEAD is disallowed if !PREEMPT.
 		 */
-#ifndef CONFIG_PREEMPT
-		WARN_ON(1);
-		return 0;
-#else
 		if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
 		    irqs_disabled()) {
 			WARN_ON(1);

@@ -229,7 +230,6 @@ static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
 		rcu_barrier_bh();
 		debug_object_free(head, &rcuhead_debug_descr);
 		return 1;
-#endif
 	default:
 		return 0;
 	}

kernel/rcutiny_plugin.h +1 -1

index 015abae..3cb8e36 100644
@@ -852,7 +852,7 @@ void exit_rcu(void)
 	if (t->rcu_read_lock_nesting == 0)
 		return;
 	t->rcu_read_lock_nesting = 1;
-	rcu_read_unlock();
+	__rcu_read_unlock();
 }
 
 #else /* #ifdef CONFIG_TINY_PREEMPT_RCU */

kernel/rcutorture.c +0 -1

index 89613f9..c224da4 100644
@@ -47,7 +47,6 @@
 #include <linux/srcu.h>
 #include <linux/slab.h>
 #include <asm/byteorder.h>
-#include <linux/sched.h>
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Paul E. McKenney <[email protected]> and "