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Commit 1d86e29b authored by Corey Minyard's avatar Corey Minyard
Browse files

ipmi: Fix a memory ordering issue 



From a locking point of view it is safe to check waiting_msg without
a lock, but there is a memory ordering issue that causes it to
possibly not be set right when viewed from another processor.  We are
already claiming a lock right after that, move the check to inside
the lock to enforce the memory ordering.

Signed-off-by: default avatarCorey Minyard <cminyard@mvista.com>
parent d6c5dc18

drivers/char/ipmi/ipmi_si_intf.c

+10 −4
Original line number Diff line number Diff line
@@ -932,9 +932,6 @@ static void sender(void *send_info, 
	enum si_sm_result result;

	unsigned long     flags;



	BUG_ON(smi_info->waiting_msg);

	smi_info->waiting_msg = msg;



	debug_timestamp("Enqueue");



	if (smi_info->run_to_completion) {
@@ -942,7 +939,7 @@ static void sender(void *send_info, 
		 * If we are running to completion, start it and run

		 * transactions until everything is clear.

		 */

		smi_info->curr_msg = smi_info->waiting_msg;

		smi_info->curr_msg = msg;

		smi_info->waiting_msg = NULL;



		/*
@@ -960,6 +957,15 @@ static void sender(void *send_info, 
	}



	spin_lock_irqsave(&smi_info->si_lock, flags);

	/*

	 * The following two lines don't need to be under the lock for

	 * the lock's sake, but they do need SMP memory barriers to

	 * avoid getting things out of order.  We are already claiming

	 * the lock, anyway, so just do it under the lock to avoid the

	 * ordering problem.

	 */

	BUG_ON(smi_info->waiting_msg);

	smi_info->waiting_msg = msg;

	check_start_timer_thread(smi_info);

	spin_unlock_irqrestore(&smi_info->si_lock, flags);

}