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lib/rbtree: set successor's parent unconditionally
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Both in Case 2 and 3, we exchange n and s.  This mean no matter whether
child2 is NULL or not, successor's parent should be assigned to node's.

This patch takes this step out to make it explicit and reduce the
ambiguity.

Besides, this step reduces some symbol size like rb_erase().

   KERN_CONFIG       upstream       patched
   OPT_FOR_PERF      877            870
   OPT_FOR_SIZE      635            621

Link: http://lkml.kernel.org/r/20191028021442.5450-1-richardw.yang@linux.intel.com
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Wei Yang authored and Linus Torvalds committed Dec 5, 2019
1 parent ae81217 commit 11d43e6
Showing 1 changed file with 1 addition and 2 deletions.
3 changes: 1 addition & 2 deletions include/linux/rbtree_augmented.h
Original file line number Diff line number Diff line change
Expand Up @@ -283,14 +283,13 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
__rb_change_child(node, successor, tmp, root);

if (child2) {
successor->__rb_parent_color = pc;
rb_set_parent_color(child2, parent, RB_BLACK);
rebalance = NULL;
} else {
unsigned long pc2 = successor->__rb_parent_color;
successor->__rb_parent_color = pc;
rebalance = __rb_is_black(pc2) ? parent : NULL;
}
successor->__rb_parent_color = pc;
tmp = successor;
}

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