s390/perf_cpum_sf: Convert to use try_cmpxchg128()

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>

diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index 72c73cfa648f1ac63c735046693274953fc7568b..0cde42f8af6ef582dc72747427655a26c58f0d4e 100644 (file)
--- 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;
        }