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linux-next/include/linux/timerqueue.h
Michel Lespinasse 4c199a93a2 rbtree: empty nodes have no color
Empty nodes have no color.  We can make use of this property to simplify
the code emitted by the RB_EMPTY_NODE and RB_CLEAR_NODE macros.  Also,
we can get rid of the rb_init_node function which had been introduced by
commit 88d19cf379 ("timers: Add rb_init_node() to allow for stack
allocated rb nodes") to avoid some issue with the empty node's color not
being initialized.

I'm not sure what the RB_EMPTY_NODE checks in rb_prev() / rb_next() are
doing there, though.  axboe introduced them in commit 10fd48f237
("rbtree: fixed reversed RB_EMPTY_NODE and rb_next/prev").  The way I
see it, the 'empty node' abstraction is only used by rbtree users to
flag nodes that they haven't inserted in any rbtree, so asking the
predecessor or successor of such nodes doesn't make any sense.

One final rb_init_node() caller was recently added in sysctl code to
implement faster sysctl name lookups.  This code doesn't make use of
RB_EMPTY_NODE at all, and from what I could see it only called
rb_init_node() under the mistaken assumption that such initialization was
required before node insertion.

[sfr@canb.auug.org.au: fix net/ceph/osd_client.c build]
Signed-off-by: Michel Lespinasse <walken@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: David Woodhouse <David.Woodhouse@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Daniel Santos <daniel.santos@pobox.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-10-09 16:22:32 +09:00

51 lines
1.1 KiB
C

#ifndef _LINUX_TIMERQUEUE_H
#define _LINUX_TIMERQUEUE_H
#include <linux/rbtree.h>
#include <linux/ktime.h>
struct timerqueue_node {
struct rb_node node;
ktime_t expires;
};
struct timerqueue_head {
struct rb_root head;
struct timerqueue_node *next;
};
extern void timerqueue_add(struct timerqueue_head *head,
struct timerqueue_node *node);
extern void timerqueue_del(struct timerqueue_head *head,
struct timerqueue_node *node);
extern struct timerqueue_node *timerqueue_iterate_next(
struct timerqueue_node *node);
/**
* timerqueue_getnext - Returns the timer with the earliest expiration time
*
* @head: head of timerqueue
*
* Returns a pointer to the timer node that has the
* earliest expiration time.
*/
static inline
struct timerqueue_node *timerqueue_getnext(struct timerqueue_head *head)
{
return head->next;
}
static inline void timerqueue_init(struct timerqueue_node *node)
{
RB_CLEAR_NODE(&node->node);
}
static inline void timerqueue_init_head(struct timerqueue_head *head)
{
head->head = RB_ROOT;
head->next = NULL;
}
#endif /* _LINUX_TIMERQUEUE_H */