[PATCH 6.12.y 1/2] s390/perf_cpum_sf: Convert to use try_cmpxchg128()

[Sasha Levin <sashal@kernel.org>]

From: Heiko Carstens <hca@linux.ibm.com>

[ Upstream commit e449399ffd295a1202b74a258227193454ef333f ]

Convert cmpxchg128() usages to try_cmpxchg128() in order to generate
slightly better code.

Reviewed-by: Juergen Christ <jchrist@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Stable-dep-of: 57ad0d4a00f5 ("s390/cpum_sf: Cap sampling rate to prevent lsctl exception")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/s390/kernel/perf_cpum_sf.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index 23a2a49547b7a..62247f20c2163 100644
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -1188,8 +1188,8 @@ static void hw_collect_samples(struct perf_event *event, unsigned long *sdbt,
 static void hw_perf_event_update(struct perf_event *event, int flush_all)
 {
 	unsigned long long event_overflow, sampl_overflow, num_sdb;
-	union hws_trailer_header old, prev, new;
 	struct hw_perf_event *hwc = &event->hw;
+	union hws_trailer_header prev, new;
 	struct hws_trailer_entry *te;
 	unsigned long *sdbt, sdb;
 	int done;
@@ -1233,13 +1233,11 @@ static void hw_perf_event_update(struct perf_event *event, int flush_all)
 		/* Reset trailer (using compare-double-and-swap) */
 		prev.val = READ_ONCE_ALIGNED_128(te->header.val);
 		do {
-			old.val = prev.val;
 			new.val = prev.val;
 			new.f = 0;
 			new.a = 1;
 			new.overflow = 0;
-			prev.val = cmpxchg128(&te->header.val, old.val, new.val);
-		} while (prev.val != old.val);
+		} while (!try_cmpxchg128(&te->header.val, &prev.val, new.val));
 
 		/* Advance to next sample-data-block */
 		sdbt++;
@@ -1405,16 +1403,15 @@ static int aux_output_begin(struct perf_output_handle *handle,
 static bool aux_set_alert(struct aux_buffer *aux, unsigned long alert_index,
 			  unsigned long long *overflow)
 {
-	union hws_trailer_header old, prev, new;
+	union hws_trailer_header prev, new;
 	struct hws_trailer_entry *te;
 
 	te = aux_sdb_trailer(aux, alert_index);
 	prev.val = READ_ONCE_ALIGNED_128(te->header.val);
 	do {
-		old.val = prev.val;
 		new.val = prev.val;
-		*overflow = old.overflow;
-		if (old.f) {
+		*overflow = prev.overflow;
+		if (prev.f) {
 			/*
 			 * SDB is already set by hardware.
 			 * Abort and try to set somewhere
@@ -1424,8 +1421,7 @@ static bool aux_set_alert(struct aux_buffer *aux, unsigned long alert_index,
 		}
 		new.a = 1;
 		new.overflow = 0;
-		prev.val = cmpxchg128(&te->header.val, old.val, new.val);
-	} while (prev.val != old.val);
+	} while (!try_cmpxchg128(&te->header.val, &prev.val, new.val));
 	return true;
 }
 
@@ -1454,7 +1450,7 @@ static bool aux_set_alert(struct aux_buffer *aux, unsigned long alert_index,
 static bool aux_reset_buffer(struct aux_buffer *aux, unsigned long range,
 			     unsigned long long *overflow)
 {
-	union hws_trailer_header old, prev, new;
+	union hws_trailer_header prev, new;
 	unsigned long i, range_scan, idx;
 	unsigned long long orig_overflow;
 	struct hws_trailer_entry *te;
@@ -1486,17 +1482,15 @@ static bool aux_reset_buffer(struct aux_buffer *aux, unsigned long range,
 		te = aux_sdb_trailer(aux, idx);
 		prev.val = READ_ONCE_ALIGNED_128(te->header.val);
 		do {
-			old.val = prev.val;
 			new.val = prev.val;
-			orig_overflow = old.overflow;
+			orig_overflow = prev.overflow;
 			new.f = 0;
 			new.overflow = 0;
 			if (idx == aux->alert_mark)
 				new.a = 1;
 			else
 				new.a = 0;
-			prev.val = cmpxchg128(&te->header.val, old.val, new.val);
-		} while (prev.val != old.val);
+		} while (!try_cmpxchg128(&te->header.val, &prev.val, new.val));
 		*overflow += orig_overflow;
 	}
 
-- 
2.53.0