Commit 3ef0296a authored Aug 15, 2013 by David Vrabel Committed by Konrad Rzeszutek Wilk Aug 20, 2013

xen/events: document behaviour when scanning the start word for events



The original comment on the scanning of the start word on the 2nd pass
did not reflect the actual behaviour (the code was incorrectly masking
bit_idx instead of the pending word itself).

The documented behaviour is not actually required since if event were
pending in the MSBs, they would be immediately scanned anyway as we go
through the loop again.

Update the documentation to reflect this (instead of trying to change
the behaviour).

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

parent e201bfcc

drivers/xen/events.c

+12 −5

Original line number	Diff line number	Diff line
		@@ -1388,14 +1388,21 @@ static void __xen_evtchn_do_upcall(void)

		pending_bits = active_evtchns(cpu, s, word_idx);
		bit_idx = 0; /* usually scan entire word from start */
		/*
		* We scan the starting word in two parts.
		*
		* 1st time: start in the middle, scanning the
		* upper bits.
		*
		* 2nd time: scan the whole word (not just the
		* parts skipped in the first pass) -- if an
		* event in the previously scanned bits is
		* pending again it would just be scanned on
		* the next loop anyway.
		*/
		if (word_idx == start_word_idx) {
		/* We scan the starting word in two parts */
		if (i == 0)
		/* 1st time: start in the middle */
		bit_idx = start_bit_idx;
		else
		/* 2nd time: mask bits done already */
		bit_idx &= (1UL << start_bit_idx) - 1;
		}

		do {

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