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Commit 20f3f3ca authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 

* 'rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  rcu: rcu_sched_grace_period(): kill the bogus flush_signals()
  rculist: use list_entry_rcu in places where it's appropriate
  rculist.h: introduce list_entry_rcu() and list_first_entry_rcu()
  rcu: Update RCU tracing documentation for __rcu_pending
  rcu: Add __rcu_pending tracing to hierarchical RCU
  RCU: make treercu be default
parents 769f3e8c 41c51c98

Documentation/RCU/trace.txt

+80 −22
Original line number Diff line number Diff line
@@ -192,23 +192,24 @@ rcu/rcuhier (which displays the struct rcu_node hierarchy). 
The output of "cat rcu/rcudata" looks as follows:



rcu:

  0 c=4011 g=4012 pq=1 pqc=4011 qp=0 rpfq=1 rp=3c2a dt=23301/73 dn=2 df=1882 of=0 ri=2126 ql=2 b=10

  1 c=4011 g=4012 pq=1 pqc=4011 qp=0 rpfq=3 rp=39a6 dt=78073/1 dn=2 df=1402 of=0 ri=1875 ql=46 b=10

  2 c=4010 g=4010 pq=1 pqc=4010 qp=0 rpfq=-5 rp=1d12 dt=16646/0 dn=2 df=3140 of=0 ri=2080 ql=0 b=10

  3 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=2b50 dt=21159/1 dn=2 df=2230 of=0 ri=1923 ql=72 b=10

  4 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=1644 dt=5783/1 dn=2 df=3348 of=0 ri=2805 ql=7 b=10

  5 c=4012 g=4013 pq=0 pqc=4011 qp=1 rpfq=3 rp=1aac dt=5879/1 dn=2 df=3140 of=0 ri=2066 ql=10 b=10

  6 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=ed8 dt=5847/1 dn=2 df=3797 of=0 ri=1266 ql=10 b=10

  7 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=1fa2 dt=6199/1 dn=2 df=2795 of=0 ri=2162 ql=28 b=10

rcu:

  0 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=10951/1 dn=0 df=1101 of=0 ri=36 ql=0 b=10

  1 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=16117/1 dn=0 df=1015 of=0 ri=0 ql=0 b=10

  2 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=1445/1 dn=0 df=1839 of=0 ri=0 ql=0 b=10

  3 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=6681/1 dn=0 df=1545 of=0 ri=0 ql=0 b=10

  4 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=1003/1 dn=0 df=1992 of=0 ri=0 ql=0 b=10

  5 c=17829 g=17830 pq=1 pqc=17829 qp=1 dt=3887/1 dn=0 df=3331 of=0 ri=4 ql=2 b=10

  6 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=859/1 dn=0 df=3224 of=0 ri=0 ql=0 b=10

  7 c=17829 g=17830 pq=0 pqc=17829 qp=1 dt=3761/1 dn=0 df=1818 of=0 ri=0 ql=2 b=10

rcu_bh:

  0 c=-268 g=-268 pq=1 pqc=-268 qp=0 rpfq=-145 rp=21d6 dt=23301/73 dn=2 df=0 of=0 ri=0 ql=0 b=10

  1 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-170 rp=20ce dt=78073/1 dn=2 df=26 of=0 ri=5 ql=0 b=10

  2 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-83 rp=fbd dt=16646/0 dn=2 df=28 of=0 ri=4 ql=0 b=10

  3 c=-268 g=-268 pq=1 pqc=-268 qp=0 rpfq=-105 rp=178c dt=21159/1 dn=2 df=28 of=0 ri=2 ql=0 b=10

  4 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-30 rp=b54 dt=5783/1 dn=2 df=32 of=0 ri=0 ql=0 b=10

  5 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-29 rp=df5 dt=5879/1 dn=2 df=30 of=0 ri=3 ql=0 b=10

  6 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-28 rp=788 dt=5847/1 dn=2 df=32 of=0 ri=0 ql=0 b=10

  7 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-53 rp=1098 dt=6199/1 dn=2 df=30 of=0 ri=3 ql=0 b=10

  0 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=10951/1 dn=0 df=0 of=0 ri=0 ql=0 b=10

  1 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=16117/1 dn=0 df=13 of=0 ri=0 ql=0 b=10

  2 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=1445/1 dn=0 df=15 of=0 ri=0 ql=0 b=10

  3 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=6681/1 dn=0 df=9 of=0 ri=0 ql=0 b=10

  4 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=1003/1 dn=0 df=15 of=0 ri=0 ql=0 b=10

  5 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=3887/1 dn=0 df=15 of=0 ri=0 ql=0 b=10

  6 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=859/1 dn=0 df=15 of=0 ri=0 ql=0 b=10

  7 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=3761/1 dn=0 df=15 of=0 ri=0 ql=0 b=10



The first section lists the rcu_data structures for rcu, the second for

rcu_bh.  Each section has one line per CPU, or eight for this 8-CPU system.
@@ -253,12 +254,6 @@ o "pqc" indicates which grace period the last-observed quiescent 
o	"qp" indicates that RCU still expects a quiescent state from

	this CPU.



o	"rpfq" is the number of rcu_pending() calls on this CPU required

	to induce this CPU to invoke force_quiescent_state().



o	"rp" is low-order four hex digits of the count of how many times

	rcu_pending() has been invoked on this CPU.



o	"dt" is the current value of the dyntick counter that is incremented

	when entering or leaving dynticks idle state, either by the

	scheduler or by irq.  The number after the "/" is the interrupt
@@ -305,6 +300,9 @@ o "b" is the batch limit for this CPU. If more than this number 
	of RCU callbacks is ready to invoke, then the remainder will

	be deferred.



There is also an rcu/rcudata.csv file with the same information in

comma-separated-variable spreadsheet format.





The output of "cat rcu/rcugp" looks as follows:
@@ -411,3 +409,63 @@ o Each element of the form "1/1 0:127 ^0" represents one struct 
		For example, the first entry at the lowest level shows

		"^0", indicating that it corresponds to bit zero in

		the first entry at the middle level.





The output of "cat rcu/rcu_pending" looks as follows:



rcu:

  0 np=255892 qsp=53936 cbr=0 cng=14417 gpc=10033 gps=24320 nf=6445 nn=146741

  1 np=261224 qsp=54638 cbr=0 cng=25723 gpc=16310 gps=2849 nf=5912 nn=155792

  2 np=237496 qsp=49664 cbr=0 cng=2762 gpc=45478 gps=1762 nf=1201 nn=136629

  3 np=236249 qsp=48766 cbr=0 cng=286 gpc=48049 gps=1218 nf=207 nn=137723

  4 np=221310 qsp=46850 cbr=0 cng=26 gpc=43161 gps=4634 nf=3529 nn=123110

  5 np=237332 qsp=48449 cbr=0 cng=54 gpc=47920 gps=3252 nf=201 nn=137456

  6 np=219995 qsp=46718 cbr=0 cng=50 gpc=42098 gps=6093 nf=4202 nn=120834

  7 np=249893 qsp=49390 cbr=0 cng=72 gpc=38400 gps=17102 nf=41 nn=144888

rcu_bh:

  0 np=146741 qsp=1419 cbr=0 cng=6 gpc=0 gps=0 nf=2 nn=145314

  1 np=155792 qsp=12597 cbr=0 cng=0 gpc=4 gps=8 nf=3 nn=143180

  2 np=136629 qsp=18680 cbr=0 cng=0 gpc=7 gps=6 nf=0 nn=117936

  3 np=137723 qsp=2843 cbr=0 cng=0 gpc=10 gps=7 nf=0 nn=134863

  4 np=123110 qsp=12433 cbr=0 cng=0 gpc=4 gps=2 nf=0 nn=110671

  5 np=137456 qsp=4210 cbr=0 cng=0 gpc=6 gps=5 nf=0 nn=133235

  6 np=120834 qsp=9902 cbr=0 cng=0 gpc=6 gps=3 nf=2 nn=110921

  7 np=144888 qsp=26336 cbr=0 cng=0 gpc=8 gps=2 nf=0 nn=118542



As always, this is once again split into "rcu" and "rcu_bh" portions.

The fields are as follows:



o	"np" is the number of times that __rcu_pending() has been invoked

	for the corresponding flavor of RCU.



o	"qsp" is the number of times that the RCU was waiting for a

	quiescent state from this CPU.



o	"cbr" is the number of times that this CPU had RCU callbacks

	that had passed through a grace period, and were thus ready

	to be invoked.



o	"cng" is the number of times that this CPU needed another

	grace period while RCU was idle.



o	"gpc" is the number of times that an old grace period had

	completed, but this CPU was not yet aware of it.



o	"gps" is the number of times that a new grace period had started,

	but this CPU was not yet aware of it.



o	"nf" is the number of times that this CPU suspected that the

	current grace period had run for too long, and thus needed to

	be forced.



	Please note that "forcing" consists of sending resched IPIs

	to holdout CPUs.  If that CPU really still is in an old RCU

	read-side critical section, then we really do have to wait for it.

	The assumption behing "forcing" is that the CPU is not still in

	an old RCU read-side critical section, but has not yet responded

	for some other reason.



o	"nn" is the number of times that this CPU needed nothing.  Alert

	readers will note that the rcu "nn" number for a given CPU very

	closely matches the rcu_bh "np" number for that same CPU.  This

	is due to short-circuit evaluation in rcu_pending().

include/linux/rculist.h

+28 −2
Original line number Diff line number Diff line
@@ -198,6 +198,32 @@ static inline void list_splice_init_rcu(struct list_head *list, 
	at->prev = last;

}



/**

 * list_entry_rcu - get the struct for this entry

 * @ptr:        the &struct list_head pointer.

 * @type:       the type of the struct this is embedded in.

 * @member:     the name of the list_struct within the struct.

 *

 * This primitive may safely run concurrently with the _rcu list-mutation

 * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().

 */

#define list_entry_rcu(ptr, type, member) \

	container_of(rcu_dereference(ptr), type, member)



/**

 * list_first_entry_rcu - get the first element from a list

 * @ptr:        the list head to take the element from.

 * @type:       the type of the struct this is embedded in.

 * @member:     the name of the list_struct within the struct.

 *

 * Note, that list is expected to be not empty.

 *

 * This primitive may safely run concurrently with the _rcu list-mutation

 * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().

 */

#define list_first_entry_rcu(ptr, type, member) \

	list_entry_rcu((ptr)->next, type, member)



#define __list_for_each_rcu(pos, head) \

	for (pos = rcu_dereference((head)->next); \

		pos != (head); \
@@ -214,9 +240,9 @@ static inline void list_splice_init_rcu(struct list_head *list, 
 * as long as the traversal is guarded by rcu_read_lock().

 */

#define list_for_each_entry_rcu(pos, head, member) \

	for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \

	for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \

		prefetch(pos->member.next), &pos->member != (head); \

		pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member))

		pos = list_entry_rcu(pos->member.next, typeof(*pos), member))





/**

include/linux/rcutree.h

+8 −1
Original line number Diff line number Diff line
@@ -161,8 +161,15 @@ struct rcu_data { 
	unsigned long offline_fqs;	/* Kicked due to being offline. */

	unsigned long resched_ipi;	/* Sent a resched IPI. */



	/* 5) For future __rcu_pending statistics. */

	/* 5) __rcu_pending() statistics. */

	long n_rcu_pending;		/* rcu_pending() calls since boot. */

	long n_rp_qs_pending;

	long n_rp_cb_ready;

	long n_rp_cpu_needs_gp;

	long n_rp_gp_completed;

	long n_rp_gp_started;

	long n_rp_need_fqs;

	long n_rp_need_nothing;



	int cpu;

};

include/linux/sched.h

+5 −3
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ struct sched_param { 
#include <linux/proportions.h>

#include <linux/seccomp.h>

#include <linux/rcupdate.h>

#include <linux/rculist.h>

#include <linux/rtmutex.h>



#include <linux/time.h>
@@ -2030,7 +2031,8 @@ static inline unsigned long wait_task_inactive(struct task_struct *p, 
}

#endif



#define next_task(p)	list_entry(rcu_dereference((p)->tasks.next), struct task_struct, tasks)

#define next_task(p) \

	list_entry_rcu((p)->tasks.next, struct task_struct, tasks)



#define for_each_process(p) \

	for (p = &init_task ; (p = next_task(p)) != &init_task ; )
@@ -2069,7 +2071,7 @@ int same_thread_group(struct task_struct *p1, struct task_struct *p2) 


static inline struct task_struct *next_thread(const struct task_struct *p)

{

	return list_entry(rcu_dereference(p->thread_group.next),

	return list_entry_rcu(p->thread_group.next,

			      struct task_struct, thread_group);

}

init/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -308,7 +308,7 @@ menu "RCU Subsystem" 


choice

	prompt "RCU Implementation"

	default CLASSIC_RCU

	default TREE_RCU



config CLASSIC_RCU

	bool "Classic RCU"