torture: Add lock_torture writer_fifo module parameter

This commit adds a module parameter that causes the locktorture writer
to run at real-time priority.

To use it:
insmod /lib/modules/torture.ko random_shuffle=1
insmod /lib/modules/locktorture.ko torture_type=mutex_lock rt_boost=1 rt_boost_factor=50 nested_locks=3 writer_fifo=1
													^^^^^^^^^^^^^

A predecessor to this patch has been helpful to uncover issues with the
proxy-execution series.

[ paulmck: Remove locktorture-specific code from kernel/torture.c. ]

Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: kernel-team@android.com
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
[jstultz: Include header change to build, reword commit message]
Signed-off-by: John Stultz <jstultz@google.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a1457995fd41cfb7db6cfa0cbb816fb9bbcd7fc0..7b94455e9ae2d21620d339d725149ad6876ad689 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2918,6 +2918,10 @@
        locktorture.torture_type= [KNL]
                        Specify the locking implementation to test.
 
+       locktorture.writer_fifo= [KNL]
+                       Run the write-side locktorture kthreads at
+                       sched_set_fifo() real-time priority.
+
        locktorture.verbose= [KNL]
                        Enable additional printk() statements.
 

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 949d3deae5062a7e1ad1ab406041cd0fecfad95c..270c7f80ce84cfc13207984593db02f4cf81f325 100644 (file)
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -45,6 +45,7 @@ torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
 torture_param(int, rt_boost, 2,
                   "Do periodic rt-boost. 0=Disable, 1=Only for rt_mutex, 2=For all lock types.");
 torture_param(int, rt_boost_factor, 50, "A factor determining how often rt-boost happens.");
+torture_param(int, writer_fifo, 0, "Run writers at sched_set_fifo() priority");
 torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
 torture_param(int, nested_locks, 0, "Number of nested locks (max = 8)");
 /* Going much higher trips "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!" errors */
@@ -809,7 +810,8 @@ static int lock_torture_writer(void *arg)
        bool skip_main_lock;
 
        VERBOSE_TOROUT_STRING("lock_torture_writer task started");
-       set_user_nice(current, MAX_NICE);
+       if (!rt_task(current))
+               set_user_nice(current, MAX_NICE);
 
        do {
                if ((torture_random(&rand) & 0xfffff) == 0)
@@ -1015,8 +1017,7 @@ static void lock_torture_cleanup(void)
 
        if (writer_tasks) {
                for (i = 0; i < cxt.nrealwriters_stress; i++)
-                       torture_stop_kthread(lock_torture_writer,
-                                            writer_tasks[i]);
+                       torture_stop_kthread(lock_torture_writer, writer_tasks[i]);
                kfree(writer_tasks);
                writer_tasks = NULL;
        }
@@ -1244,8 +1245,9 @@ static int __init lock_torture_init(void)
                        goto create_reader;
 
                /* Create writer. */
-               firsterr = torture_create_kthread(lock_torture_writer, &cxt.lwsa[i],
-                                                 writer_tasks[i]);
+               firsterr = torture_create_kthread_cb(lock_torture_writer, &cxt.lwsa[i],
+                                                    writer_tasks[i],
+                                                    writer_fifo ? sched_set_fifo : NULL);
                if (torture_init_error(firsterr))
                        goto unwind;
 

diff --git a/kernel/torture.c b/kernel/torture.c
index b88a1a86d9dafaa062fed5ff1db6ac7df36a7f95..a1ac493488e228daa18bbd886529e93386590ca4 100644 (file)
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -37,6 +37,7 @@
 #include <linux/ktime.h>
 #include <asm/byteorder.h>
 #include <linux/torture.h>
+#include <linux/sched/rt.h>
 #include "rcu/rcu.h"
 
 MODULE_LICENSE("GPL");
@@ -734,7 +735,7 @@ bool stutter_wait(const char *title)
        cond_resched_tasks_rcu_qs();
        spt = READ_ONCE(stutter_pause_test);
        for (; spt; spt = READ_ONCE(stutter_pause_test)) {
-               if (!ret) {
+               if (!ret && !rt_task(current)) {
                        sched_set_normal(current, MAX_NICE);
                        ret = true;
                }