Merge branch 'rcu-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip (b922df73) · Commits · 戴 / test

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 */

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