From: Tvrtko Ursulin <tvrtko.ursu...@intel.com>

Back when gem_wsim used forking it was safe to use the common storage
prng, but after converting to threads it no longer is.

Fix by storing and using a new per workload seed for batch buffer
duration randomness.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
---
 benchmarks/gem_wsim.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/benchmarks/gem_wsim.c b/benchmarks/gem_wsim.c
index 0ccb271575f7..c43bbbc8c94d 100644
--- a/benchmarks/gem_wsim.c
+++ b/benchmarks/gem_wsim.c
@@ -193,6 +193,7 @@ struct workload
        unsigned int flags;
        bool print_stats;
 
+       uint32_t bb_prng;
        uint32_t prng;
 
        struct timespec repeat_start;
@@ -240,6 +241,8 @@ struct workload
 static const unsigned int nop_calibration_us = 1000;
 static unsigned long nop_calibration;
 
+static unsigned int master_prng;
+
 static unsigned int context_vcs_rr;
 
 static int verbose = 1;
@@ -1067,14 +1070,14 @@ clone_workload(struct workload *_wrk)
 #define PAGE_SIZE (4096)
 #endif
 
-static unsigned int get_duration(struct w_step *w)
+static unsigned int get_duration(struct workload *wrk, struct w_step *w)
 {
        struct duration *dur = &w->duration;
 
        if (dur->min == dur->max)
                return dur->min;
        else
-               return dur->min + hars_petruska_f54_1_random_unsafe() %
+               return dur->min + hars_petruska_f54_1_random(&wrk->bb_prng) %
                       (dur->max + 1 - dur->min);
 }
 
@@ -1448,6 +1451,7 @@ prepare_workload(unsigned int id, struct workload *wrk, 
unsigned int flags)
 
        wrk->id = id;
        wrk->prng = rand();
+       wrk->bb_prng = (wrk->flags & SYNCEDCLIENTS) ? master_prng : rand();
        wrk->run = true;
 
        ctx_vcs =  0;
@@ -2607,7 +2611,7 @@ do_eb(struct workload *wrk, struct w_step *w, enum 
intel_engine_id engine,
        w->eb.batch_start_offset =
                w->unbound_duration ?
                0 :
-               ALIGN(w->bb_sz - get_bb_sz(get_duration(w)),
+               ALIGN(w->bb_sz - get_bb_sz(get_duration(wrk, w)),
                      2 * sizeof(uint32_t));
 
        for (i = 0; i < w->fence_deps.nr; i++) {
@@ -2676,9 +2680,6 @@ static void *run_workload(void *data)
 
        clock_gettime(CLOCK_MONOTONIC, &t_start);
 
-       hars_petruska_f54_1_random_seed((wrk->flags & SYNCEDCLIENTS) ?
-                                       0 : wrk->id);
-
        init_status_page(wrk, INIT_ALL);
        for (count = 0; wrk->run && (wrk->background || count < wrk->repeat);
             count++) {
@@ -3117,6 +3118,10 @@ int main(int argc, char **argv)
 
        init_clocks();
 
+       master_prng = time(NULL);
+       srand(master_prng);
+       master_prng = rand();
+
        while ((c = getopt(argc, argv,
                           "hqv2RsSHxGdc:n:r:w:W:a:t:b:p:")) != -1) {
                switch (c) {
-- 
2.20.1

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