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Commit b922df73 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'rcu-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 

* 'rcu-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (21 commits)
  rcu: RCU-based detection of stalled CPUs for Classic RCU, fix
  rcu: RCU-based detection of stalled CPUs for Classic RCU
  rcu: add rcu_read_lock_sched() / rcu_read_unlock_sched()
  rcu: fix sparse shadowed variable warning
  doc/RCU: fix pseudocode in rcuref.txt
  rcuclassic: fix compiler warning
  rcu: use irq-safe locks
  rcuclassic: fix compilation NG
  rcu: fix locking cleanup fallout
  rcu: remove redundant ACCESS_ONCE definition from rcupreempt.c
  rcu: fix classic RCU locking cleanup lockdep problem
  rcu: trace fix possible mem-leak
  rcu: just rename call_rcu_bh instead of making it a macro
  rcu: remove list_for_each_rcu()
  rcu: fixes to include/linux/rcupreempt.h
  rcu: classic RCU locking and memory-barrier cleanups
  rcu: prevent console flood when one CPU sees another AWOL via RCU
  rcu, debug: detect stalled grace periods, cleanups
  rcu, debug: detect stalled grace periods
  rcu classic: new algorithm for callbacks-processing(v2)
  ...
parents c54dcd8e cdbb92b3

Documentation/RCU/checklist.txt

+1 −1
Original line number Diff line number Diff line
@@ -210,7 +210,7 @@ over a rather long period of time, but improvements are always welcome! 
		number of updates per grace period.



9.	All RCU list-traversal primitives, which include

	rcu_dereference(), list_for_each_rcu(), list_for_each_entry_rcu(),

	rcu_dereference(), list_for_each_entry_rcu(),

	list_for_each_continue_rcu(), and list_for_each_safe_rcu(),

	must be either within an RCU read-side critical section or

	must be protected by appropriate update-side locks.  RCU

Documentation/RCU/rcuref.txt

+8 −8
Original line number Diff line number Diff line
@@ -29,9 +29,9 @@ release_referenced() delete() 
					}



If this list/array is made lock free using RCU as in changing the

write_lock() in add() and delete() to spin_lock and changing read_lock

in search_and_reference to rcu_read_lock(), the atomic_get in

search_and_reference could potentially hold reference to an element which

write_lock() in add() and delete() to spin_lock() and changing read_lock()

in search_and_reference() to rcu_read_lock(), the atomic_inc() in

search_and_reference() could potentially hold reference to an element which

has already been deleted from the list/array.  Use atomic_inc_not_zero()

in this scenario as follows:
@@ -40,20 +40,20 @@ add() search_and_reference() 
{					{

    alloc_object			    rcu_read_lock();

    ...					    search_for_element

    atomic_set(&el->rc, 1);		    if (atomic_inc_not_zero(&el->rc)) {

    write_lock(&list_lock);		        rcu_read_unlock();

    atomic_set(&el->rc, 1);		    if (!atomic_inc_not_zero(&el->rc)) {

    spin_lock(&list_lock);		        rcu_read_unlock();

					        return FAIL;

    add_element				    }

    ...					    ...

    write_unlock(&list_lock);		    rcu_read_unlock();

    spin_unlock(&list_lock);		    rcu_read_unlock();

}					}

3.					4.

release_referenced()			delete()

{					{

    ...					    write_lock(&list_lock);

    ...					    spin_lock(&list_lock);

    if (atomic_dec_and_test(&el->rc))       ...

        call_rcu(&el->head, el_free);       delete_element

    ...                                     write_unlock(&list_lock);

    ...                                     spin_unlock(&list_lock);

} 					    ...

					    if (atomic_dec_and_test(&el->rc))

					        call_rcu(&el->head, el_free);

Documentation/RCU/whatisRCU.txt

+0 −2
Original line number Diff line number Diff line
@@ -786,8 +786,6 @@ RCU pointer/list traversal: 
	list_for_each_entry_rcu

	hlist_for_each_entry_rcu



	list_for_each_rcu		(to be deprecated in favor of

					 list_for_each_entry_rcu)

	list_for_each_continue_rcu	(to be deprecated in favor of new

					 list_for_each_entry_continue_rcu)

include/linux/compiler.h

+3 −1
Original line number Diff line number Diff line
@@ -190,7 +190,9 @@ extern void __chk_io_ptr(const volatile void __iomem *); 
 * ACCESS_ONCE() in different C statements.

 *

 * This macro does absolutely -nothing- to prevent the CPU from reordering,

 * merging, or refetching absolutely anything at any time.

 * merging, or refetching absolutely anything at any time.  Its main intended

 * use is to mediate communication between process-level code and irq/NMI

 * handlers, all running on the same CPU.

 */

#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))

include/linux/rcuclassic.h

+27 −10
Original line number Diff line number Diff line
@@ -40,12 +40,21 @@ 
#include <linux/cpumask.h>

#include <linux/seqlock.h>



#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

#define RCU_SECONDS_TILL_STALL_CHECK	( 3 * HZ) /* for rcp->jiffies_stall */

#define RCU_SECONDS_TILL_STALL_RECHECK	(30 * HZ) /* for rcp->jiffies_stall */

#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */



/* Global control variables for rcupdate callback mechanism. */

struct rcu_ctrlblk {

	long	cur;		/* Current batch number.                      */

	long	completed;	/* Number of the last completed batch         */

	int	next_pending;	/* Is the next batch already waiting?         */

	long	pending;	/* Number of the last pending batch           */

#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

	unsigned long gp_start;	/* Time at which GP started in jiffies. */

	unsigned long jiffies_stall;

				/* Time at which to check for CPU stalls. */

#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */



	int	signaled;
@@ -66,11 +75,7 @@ static inline int rcu_batch_after(long a, long b) 
	return (a - b) > 0;

}



/*

 * Per-CPU data for Read-Copy UPdate.

 * nxtlist - new callbacks are added here

 * curlist - current batch for which quiescent cycle started if any

 */

/* Per-CPU data for Read-Copy UPdate. */

struct rcu_data {

	/* 1) quiescent state handling : */

	long		quiescbatch;     /* Batch # for grace period */
@@ -78,12 +83,24 @@ struct rcu_data { 
	int		qs_pending;	 /* core waits for quiesc state */



	/* 2) batch handling */

	long  	       	batch;           /* Batch # for current RCU batch */

	/*

	 * if nxtlist is not NULL, then:

	 * batch:

	 *	The batch # for the last entry of nxtlist

	 * [*nxttail[1], NULL = *nxttail[2]):

	 *	Entries that batch # <= batch

	 * [*nxttail[0], *nxttail[1]):

	 *	Entries that batch # <= batch - 1

	 * [nxtlist, *nxttail[0]):

	 *	Entries that batch # <= batch - 2

	 *	The grace period for these entries has completed, and

	 *	the other grace-period-completed entries may be moved

	 *	here temporarily in rcu_process_callbacks().

	 */

	long  	       	batch;

	struct rcu_head *nxtlist;

	struct rcu_head **nxttail;

	struct rcu_head **nxttail[3];

	long            qlen; 	 	 /* # of queued callbacks */

	struct rcu_head *curlist;

	struct rcu_head **curtail;

	struct rcu_head *donelist;

	struct rcu_head **donetail;

	long		blimit;		 /* Upper limit on a processed batch */