ef2e64035f
commit 511885d7061eda3eb1faf3f57dcc936ff75863f1 upstream. Simplify the timerqueue code by using cached rbtrees and rely on the tree leftmost node semantics to get the timer with earliest expiration time. This is a drop in conversion, and therefore semantics remain untouched. The runtime overhead of cached rbtrees is be pretty much the same as the current head->next method, noting that when removing the leftmost node, a common operation for the timerqueue, the rb_next(leftmost) is O(1) as well, so the next timer will either be the right node or its parent. Therefore no extra pointer chasing. Finally, the size of the struct timerqueue_head remains the same. Passes several hours of rcutorture. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20190724152323.bojciei3muvfxalm@linux-r8p5 [bwh: While this was supposed to be just refactoring, it also fixed a security flaw (CVE-2021-20317). Backported to 4.9: - Deleted code in timerqueue_del() is different before commit d852d39432f5 "timerqueue: Use rb_entry_safe() instead of open-coding it" - Adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
50 lines
1.1 KiB
C
50 lines
1.1 KiB
C
#ifndef _LINUX_TIMERQUEUE_H
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#define _LINUX_TIMERQUEUE_H
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#include <linux/rbtree.h>
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#include <linux/ktime.h>
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struct timerqueue_node {
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struct rb_node node;
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ktime_t expires;
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};
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struct timerqueue_head {
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struct rb_root_cached rb_root;
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};
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extern bool timerqueue_add(struct timerqueue_head *head,
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struct timerqueue_node *node);
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extern bool timerqueue_del(struct timerqueue_head *head,
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struct timerqueue_node *node);
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extern struct timerqueue_node *timerqueue_iterate_next(
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struct timerqueue_node *node);
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/**
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* timerqueue_getnext - Returns the timer with the earliest expiration time
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*
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* @head: head of timerqueue
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*
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* Returns a pointer to the timer node that has the earliest expiration time.
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*/
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static inline
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struct timerqueue_node *timerqueue_getnext(struct timerqueue_head *head)
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{
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struct rb_node *leftmost = rb_first_cached(&head->rb_root);
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return rb_entry(leftmost, struct timerqueue_node, node);
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}
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static inline void timerqueue_init(struct timerqueue_node *node)
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{
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RB_CLEAR_NODE(&node->node);
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}
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static inline void timerqueue_init_head(struct timerqueue_head *head)
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{
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head->rb_root = RB_ROOT_CACHED;
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}
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#endif /* _LINUX_TIMERQUEUE_H */
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