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authorDavid Vrabel <david.vrabel@citrix.com>2013-08-15 13:21:05 +0100
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-08-20 10:15:28 -0400
commit3ef0296a0b77d70585e23be93a5144e764a2781e (patch)
tree1fea4c08b58d175328176b5d297c44651ac532ae /drivers/xen
parente201bfcc5c4fe6d58ce2b21fb4f4c2a2f0ab7ab8 (diff)
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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>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/events.c17
1 files changed, 12 insertions, 5 deletions
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index c8b9d9f..0b14a9bb 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -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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