Commit b8f2ed53 authored Aug 23, 2016 by Paul E. McKenney

rcu: Tighten up __call_rcu() rcu_head alignment check



Commit 720abae3 ("rcu: force alignment on struct
callback_head/rcu_head") forced the rcu_head (AKA callback_head)
structure's alignment to pointer size, that is, to 4-byte boundaries on
32-bit systems and to 8-byte boundaries on 64-bit systems.  This
commit therefore checks for this same alignment in __call_rcu(),
which used to contain a looser check for two-byte alignment.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

parent 1001354c

kernel/rcu/tree.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -3121,7 +3121,9 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func,
		unsigned long flags;
		struct rcu_data *rdp;

		WARN_ON_ONCE((unsigned long)head & 0x1); /* Misaligned rcu_head! */
		/* Misaligned rcu_head! */
		WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1));

		if (debug_rcu_head_queue(head)) {
		/* Probable double call_rcu(), so leak the callback. */
		WRITE_ONCE(head->func, rcu_leak_callback);

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