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[tip/core/rcu,04/47] rcu: Add diagnostic for misaligned rcu_head structures

Message ID 1328319922-30828-4-git-send-email-paulmck@linux.vnet.ibm.com
State Accepted
Commit 0bb7b59d6e2b8440cd7097097dd4bbfc4d76ed07
Headers show

Commit Message

Paul E. McKenney Feb. 4, 2012, 1:44 a.m. UTC 
From: "Paul E. McKenney" <paul.mckenney@linaro.org>

The push for energy efficiency will require that RCU tag rcu_head
structures to indicate whether or not their invocation is time critical.
This tagging is best carried out in the bottom bits of the ->next
pointers in the rcu_head structures.  This tagging requires that the
rcu_head structures be properly aligned, so this commit adds the required
diagnostics.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutree.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
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Patch

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 3cf713a..570f753 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1707,6 +1707,7 @@  __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
 	unsigned long flags;
 	struct rcu_data *rdp;
 
+	WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */
 	debug_rcu_head_queue(head);
 	head->func = func;
 	head->next = NULL;