Commit 5e02c749 authored by Heiko Carstens's avatar Heiko Carstens
Browse files

s390/cpum_sf: use READ_ONCE_ALIGNED_128() instead of 128-bit cmpxchg 

Use READ_ONCE_ALIGNED_128() to read the previous value in front of a
128-bit cmpxchg loop, instead of (mis-)using a 128-bit cmpxchg operation to
do the same.

This makes the code more readable and is faster.

Link: https://lore.kernel.org/r/20230224100237.3247871-3-hca@linux.ibm.com


Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 434b2660

arch/s390/kernel/perf_cpum_sf.c

+3 −6
Original line number Diff line number Diff line
@@ -1355,8 +1355,7 @@ static void hw_perf_event_update(struct perf_event *event, int flush_all) 
		num_sdb++;



		/* Reset trailer (using compare-double-and-swap) */

		/* READ_ONCE() 16 byte header */

		prev.val = __cdsg(&te->header.val, 0, 0);

		prev.val = READ_ONCE_ALIGNED_128(te->header.val);

		do {

			old.val = prev.val;

			new.val = prev.val;
@@ -1558,8 +1557,7 @@ static bool aux_set_alert(struct aux_buffer *aux, unsigned long alert_index, 
	struct hws_trailer_entry *te;



	te = aux_sdb_trailer(aux, alert_index);

	/* READ_ONCE() 16 byte header */

	prev.val = __cdsg(&te->header.val, 0, 0);

	prev.val = READ_ONCE_ALIGNED_128(te->header.val);

	do {

		old.val = prev.val;

		new.val = prev.val;
@@ -1637,8 +1635,7 @@ static bool aux_reset_buffer(struct aux_buffer *aux, unsigned long range, 
	idx_old = idx = aux->empty_mark + 1;

	for (i = 0; i < range_scan; i++, idx++) {

		te = aux_sdb_trailer(aux, idx);

		/* READ_ONCE() 16 byte header */

		prev.val = __cdsg(&te->header.val, 0, 0);

		prev.val = READ_ONCE_ALIGNED_128(te->header.val);

		do {

			old.val = prev.val;

			new.val = prev.val;