refscale: Ditch ref_scale_shutdown in favor of torture_shutdown_init()

The torture_shutdown_init() function spawns a shutdown kthread in
a manner very similar to that implemented by ref_scale_shutdown().
This commit therefore re-implements ref_scale_shutdown in terms of
torture_shutdown_init().

The initial draft of this patch was generated by version 2.1.16 of the
Claude AI/LLM, but trained and configured for use by my employer, and
prompted to refer to Linux-kernel source code.  This initial draft failed
to provide a forward reference to ref_scale_cleanup(), passed zero to
torture_shutdown_init() for an unwelcome insta-shutdown, and failed to
pass the kvm.sh --duration argument in as a refscale module parameter.
On the other hand, it did catch the need to NULL main_task on the
post-test self-shutdown code path, which I might well have forgotten
to do.

This version of the patch fixes those problems, and in fact very little
of the initial draft remains.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index c158b6a947cdef6f3f0687bb6d73d95694ded03a..a2d9d75d88a10df3d679331fad71e4399bb4a0f0 100644 (file)
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -92,15 +92,9 @@ torture_param(int, nreaders, -1, "Number of readers, -1 for 75% of CPUs.");
 torture_param(int, nruns, 30, "Number of experiments to run.");
 // Reader delay in nanoseconds, 0 for no delay.
 torture_param(int, readdelay, 0, "Read-side delay in nanoseconds.");
-
-#ifdef MODULE
-# define REFSCALE_SHUTDOWN 0
-#else
-# define REFSCALE_SHUTDOWN 1
-#endif
-
-torture_param(bool, shutdown, REFSCALE_SHUTDOWN,
-             "Shutdown at end of scalability tests.");
+// Maximum shutdown delay in seconds, or zero for no shutdown.
+torture_param(int, shutdown_secs, !IS_MODULE(CONFIG_REPRO_TEST) * 300,
+             "Shutdown at end of scalability tests or at specified timeout (s).");
 
 struct reader_task {
        struct task_struct *task;
@@ -109,12 +103,8 @@ struct reader_task {
        u64 last_duration_ns;
 };
 
-static struct task_struct *shutdown_task;
-static wait_queue_head_t shutdown_wq;
-
 static struct task_struct *main_task;
 static wait_queue_head_t main_wq;
-static int shutdown_start;
 
 static struct reader_task *reader_tasks;
 
@@ -1357,6 +1347,8 @@ static u64 process_durations(int n)
        return sum;
 }
 
+static void ref_scale_cleanup(void);
+
 // The main_func is the main orchestrator, it performs a bunch of
 // experiments.  For every experiment, it orders all the readers
 // involved to start and waits for them to finish the experiment. It
@@ -1443,9 +1435,10 @@ static int main_func(void *arg)
 
 oom_exit:
        // This will shutdown everything including us.
-       if (shutdown) {
-               shutdown_start = 1;
-               wake_up(&shutdown_wq);
+       if (shutdown_secs) {
+               main_task = NULL;  // Avoid self-kill deadlock.
+               ref_scale_cleanup();
+               kernel_power_off();
        }
 
        // Wait for torture to stop us
@@ -1463,8 +1456,8 @@ static void
 ref_scale_print_module_parms(const struct ref_scale_ops *cur_ops, const char *tag)
 {
        pr_alert("%s" SCALE_FLAG
-                "--- %s:  verbose=%d verbose_batched=%d shutdown=%d holdoff=%d lookup_instances=%ld loops=%d nreaders=%d nruns=%d readdelay=%d\n", scale_type, tag,
-                verbose, verbose_batched, shutdown, holdoff, lookup_instances, loops, nreaders, nruns, readdelay);
+                "--- %s:  verbose=%d verbose_batched=%d shutdown_secs=%d holdoff=%d lookup_instances=%ld loops=%d nreaders=%d nruns=%d readdelay=%d\n", scale_type, tag,
+                verbose, verbose_batched, shutdown_secs, holdoff, lookup_instances, loops, nreaders, nruns, readdelay);
 }
 
 static void
@@ -1497,19 +1490,6 @@ ref_scale_cleanup(void)
        torture_cleanup_end();
 }
 
-// Shutdown kthread.  Just waits to be awakened, then shuts down system.
-static int
-ref_scale_shutdown(void *arg)
-{
-       wait_event_idle(shutdown_wq, shutdown_start);
-
-       smp_mb(); // Wake before output.
-       ref_scale_cleanup();
-       kernel_power_off();
-
-       return -EINVAL;
-}
-
 static int __init
 ref_scale_init(void)
 {
@@ -1553,13 +1533,10 @@ ref_scale_init(void)
        ref_scale_print_module_parms(cur_ops, "Start of test");
 
        // Shutdown task
-       if (shutdown) {
-               init_waitqueue_head(&shutdown_wq);
-               firsterr = torture_create_kthread(ref_scale_shutdown, NULL,
-                                                 shutdown_task);
+       if (shutdown_secs) {
+               firsterr = torture_shutdown_init(shutdown_secs, ref_scale_cleanup);
                if (torture_init_error(firsterr))
                        goto unwind;
-               schedule_timeout_uninterruptible(1);
        }
 
        // Reader tasks (default to ~75% of online CPUs).
@@ -1604,7 +1581,7 @@ ref_scale_init(void)
 unwind:
        torture_init_end();
        ref_scale_cleanup();
-       if (shutdown) {
+       if (shutdown_secs) {
                WARN_ON(!IS_MODULE(CONFIG_RCU_REF_SCALE_TEST));
                kernel_power_off();
        }

diff --git a/tools/testing/selftests/rcutorture/configs/refscale/ver_functions.sh b/tools/testing/selftests/rcutorture/configs/refscale/ver_functions.sh
index 7484656276012239e5d846a7365ef3203e46db2c..219fac070af28d9f3e058a91d5fbc4d36659decd 100644 (file)
--- a/tools/testing/selftests/rcutorture/configs/refscale/ver_functions.sh
+++ b/tools/testing/selftests/rcutorture/configs/refscale/ver_functions.sh
@@ -11,7 +11,7 @@
 #
 # Adds per-version torture-module parameters to kernels supporting them.
 per_version_boot_params () {
-       echo    refscale.shutdown=1 \
+       echo    refscale.shutdown_secs=$3 \
                refscale.verbose=0 \
                $1
 }