An interesting observation made with our parallel selftests was that on
our small/single cpu systems we would call kthread_stop() before the
kthreads were spawned. If this happens, the kthread is never run at all;
completely bypassing the test.
A simple yield() from the parent will ensure that all children have the
opportunity to start before we reap them.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
---
drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c | 2 ++
drivers/gpu/drm/i915/gem/selftests/i915_gem_object_blt.c | 2 ++
drivers/gpu/drm/i915/gt/selftest_hangcheck.c | 2 ++
drivers/gpu/drm/i915/gt/selftest_lrc.c | 2 ++
drivers/gpu/drm/i915/selftests/i915_request.c | 2 ++
5 files changed, 10 insertions(+)
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
index c6e61564bb5e..62fabc023a83 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
@@ -345,6 +345,8 @@ static int live_parallel_switch(void *arg)
get_task_struct(data[n].tsk);
}
+ yield(); /* start all threads before we kthread_stop() */
+
for (n = 0; n < count; n++) {
int status;
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_object_blt.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_object_blt.c
index ac40c704514e..e8132aca0bb6 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_object_blt.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_object_blt.c
@@ -473,6 +473,8 @@ static int igt_threaded_blt(struct drm_i915_private *i915,
get_task_struct(tsk[i]);
}
+ yield(); /* start all threads before we kthread_stop() */
+
for (i = 0; i < n_cpus; ++i) {
int status;
diff --git a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
index 8abc0a1d692b..85e9ccf5c304 100644
--- a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
+++ b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
@@ -826,6 +826,8 @@ static int __igt_reset_engines(struct intel_gt *gt,
get_task_struct(tsk);
}
+ yield(); /* start all threads before we begin */
+
intel_engine_pm_get(engine);
set_bit(I915_RESET_ENGINE + id, >->reset.flags);
do {
diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
index 5e8c365548f0..eb71ac2f992c 100644
--- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
+++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
@@ -2252,6 +2252,8 @@ static int smoke_crescendo(struct preempt_smoke *smoke, unsigned int flags)
get_task_struct(tsk[id]);
}
+ yield(); /* start all threads before we kthread_stop() */
+
count = 0;
for_each_engine(engine, smoke->gt, id) {
int status;
diff --git a/drivers/gpu/drm/i915/selftests/i915_request.c b/drivers/gpu/drm/i915/selftests/i915_request.c
index 74788980ca7a..ef350ff3c35c 100644
--- a/drivers/gpu/drm/i915/selftests/i915_request.c
+++ b/drivers/gpu/drm/i915/selftests/i915_request.c
@@ -465,6 +465,7 @@ static int mock_breadcrumbs_smoketest(void *arg)
get_task_struct(threads[n]);
}
+ yield(); /* start all threads before we begin */
msleep(jiffies_to_msecs(i915_selftest.timeout_jiffies));
for (n = 0; n < ncpus; n++) {
@@ -1392,6 +1393,7 @@ static int live_breadcrumbs_smoketest(void *arg)
idx++;
}
+ yield(); /* start all threads before we begin */
msleep(jiffies_to_msecs(i915_selftest.timeout_jiffies));
out_flush:
--
2.24.0.rc2
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