Merge branches 'doc.2016.06.15a', 'fixes.2016.06.15b' and 'torture.2016.06.14a' into HEAD
doc.2016.06.15a: Documentation updates
fixes.2016.06.15b: Documentation updates
torture.2016.06.14a: Documentation updates
diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html
index e7e24b3..ece410f 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.html
+++ b/Documentation/RCU/Design/Requirements/Requirements.html
@@ -2391,6 +2391,41 @@
idle-loop code.
Steven Rostedt supplied <tt>_rcuidle</tt> event tracing,
which is used quite heavily in the idle loop.
+However, there are some restrictions on the code placed within
+<tt>RCU_NONIDLE()</tt>:
+
+<ol>
+<li> Blocking is prohibited.
+ In practice, this is not a serious restriction given that idle
+ tasks are prohibited from blocking to begin with.
+<li> Although nesting <tt>RCU_NONIDLE()</tt> is permited, they cannot
+ nest indefinitely deeply.
+ However, given that they can be nested on the order of a million
+ deep, even on 32-bit systems, this should not be a serious
+ restriction.
+ This nesting limit would probably be reached long after the
+ compiler OOMed or the stack overflowed.
+<li> Any code path that enters <tt>RCU_NONIDLE()</tt> must sequence
+ out of that same <tt>RCU_NONIDLE()</tt>.
+ For example, the following is grossly illegal:
+
+ <blockquote>
+ <pre>
+ 1 RCU_NONIDLE({
+ 2 do_something();
+ 3 goto bad_idea; /* BUG!!! */
+ 4 do_something_else();});
+ 5 bad_idea:
+ </pre>
+ </blockquote>
+
+ <p>
+ It is just as illegal to transfer control into the middle of
+ <tt>RCU_NONIDLE()</tt>'s argument.
+ Yes, in theory, you could transfer in as long as you also
+ transferred out, but in practice you could also expect to get sharply
+ worded review comments.
+</ol>
<p>
It is similarly socially unacceptable to interrupt an
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index 0f7fb42..e93d041 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -49,7 +49,7 @@
This boot/sysfs parameter controls the RCU-tasks stall warning
interval. A value of zero or less suppresses RCU-tasks stall
warnings. A positive value sets the stall-warning interval
- in jiffies. An RCU-tasks stall warning starts wtih the line:
+ in jiffies. An RCU-tasks stall warning starts with the line:
INFO: rcu_tasks detected stalls on tasks:
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index 111770f..2044227 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -5,6 +5,9 @@
2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
+ 2010 Big API Table http://lwn.net/Articles/419086/
+5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
+ 2014 Big API Table http://lwn.net/Articles/609973/
What is RCU?
diff --git a/include/linux/torture.h b/include/linux/torture.h
index 7759fc3..6685a73 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -50,6 +50,10 @@
do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! %s\n", torture_type, s); } while (0)
/* Definitions for online/offline exerciser. */
+bool torture_offline(int cpu, long *n_onl_attempts, long *n_onl_successes,
+ unsigned long *sum_offl, int *min_onl, int *max_onl);
+bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
+ unsigned long *sum_onl, int *min_onl, int *max_onl);
int torture_onoff_init(long ooholdoff, long oointerval);
void torture_onoff_stats(void);
bool torture_onoff_failures(void);
diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
index 3cee0d8..d38ab08 100644
--- a/kernel/rcu/rcuperf.c
+++ b/kernel/rcu/rcuperf.c
@@ -58,7 +58,7 @@
#define VERBOSE_PERFOUT_ERRSTRING(s) \
do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)
-torture_param(bool, gp_exp, true, "Use expedited GP wait primitives");
+torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
torture_param(int, nreaders, -1, "Number of RCU reader threads");
torture_param(int, nwriters, -1, "Number of RCU updater threads");
@@ -96,12 +96,7 @@
#define MAX_MEAS 10000
#define MIN_MEAS 100
-#if defined(MODULE) || defined(CONFIG_RCU_PERF_TEST_RUNNABLE)
-#define RCUPERF_RUNNABLE_INIT 1
-#else
-#define RCUPERF_RUNNABLE_INIT 0
-#endif
-static int perf_runnable = RCUPERF_RUNNABLE_INIT;
+static int perf_runnable = IS_ENABLED(MODULE);
module_param(perf_runnable, int, 0444);
MODULE_PARM_DESC(perf_runnable, "Start rcuperf at boot");
@@ -363,8 +358,6 @@
u64 *wdpp = writer_durations[me];
VERBOSE_PERFOUT_STRING("rcu_perf_writer task started");
- WARN_ON(rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp);
- WARN_ON(rcu_gp_is_normal() && gp_exp);
WARN_ON(!wdpp);
set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
sp.sched_priority = 1;
@@ -631,12 +624,24 @@
firsterr = -ENOMEM;
goto unwind;
}
+ if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp) {
+ VERBOSE_PERFOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!");
+ firsterr = -EINVAL;
+ goto unwind;
+ }
+ if (rcu_gp_is_normal() && gp_exp) {
+ VERBOSE_PERFOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!");
+ firsterr = -EINVAL;
+ goto unwind;
+ }
for (i = 0; i < nrealwriters; i++) {
writer_durations[i] =
kcalloc(MAX_MEAS, sizeof(*writer_durations[i]),
GFP_KERNEL);
- if (!writer_durations[i])
+ if (!writer_durations[i]) {
+ firsterr = -ENOMEM;
goto unwind;
+ }
firsterr = torture_create_kthread(rcu_perf_writer, (void *)i,
writer_tasks[i]);
if (firsterr)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 60bd533..971e2b1 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -182,12 +182,7 @@
return rcu_torture_writer_state_names[i];
}
-#if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
-#define RCUTORTURE_RUNNABLE_INIT 1
-#else
-#define RCUTORTURE_RUNNABLE_INIT 0
-#endif
-static int torture_runnable = RCUTORTURE_RUNNABLE_INIT;
+static int torture_runnable = IS_ENABLED(MODULE);
module_param(torture_runnable, int, 0444);
MODULE_PARM_DESC(torture_runnable, "Start rcutorture at boot");
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 534c590..0082fce 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -79,8 +79,6 @@
pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n");
if (IS_ENABLED(CONFIG_PROVE_RCU))
pr_info("\tRCU lockdep checking is enabled.\n");
- if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_RUNNABLE))
- pr_info("\tRCU torture testing starts during boot.\n");
if (RCU_NUM_LVLS >= 4)
pr_info("\tFour(or more)-level hierarchy is enabled.\n");
if (RCU_FANOUT_LEAF != 16)
diff --git a/kernel/torture.c b/kernel/torture.c
index fa0bdee..75961b3 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -82,6 +82,104 @@
static int max_online;
/*
+ * Attempt to take a CPU offline. Return false if the CPU is already
+ * offline or if it is not subject to CPU-hotplug operations. The
+ * caller can detect other failures by looking at the statistics.
+ */
+bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
+ unsigned long *sum_offl, int *min_offl, int *max_offl)
+{
+ unsigned long delta;
+ int ret;
+ unsigned long starttime;
+
+ if (!cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
+ return false;
+
+ if (verbose)
+ pr_alert("%s" TORTURE_FLAG
+ "torture_onoff task: offlining %d\n",
+ torture_type, cpu);
+ starttime = jiffies;
+ (*n_offl_attempts)++;
+ ret = cpu_down(cpu);
+ if (ret) {
+ if (verbose)
+ pr_alert("%s" TORTURE_FLAG
+ "torture_onoff task: offline %d failed: errno %d\n",
+ torture_type, cpu, ret);
+ } else {
+ if (verbose)
+ pr_alert("%s" TORTURE_FLAG
+ "torture_onoff task: offlined %d\n",
+ torture_type, cpu);
+ (*n_offl_successes)++;
+ delta = jiffies - starttime;
+ sum_offl += delta;
+ if (*min_offl < 0) {
+ *min_offl = delta;
+ *max_offl = delta;
+ }
+ if (*min_offl > delta)
+ *min_offl = delta;
+ if (*max_offl < delta)
+ *max_offl = delta;
+ }
+
+ return true;
+}
+EXPORT_SYMBOL_GPL(torture_offline);
+
+/*
+ * Attempt to bring a CPU online. Return false if the CPU is already
+ * online or if it is not subject to CPU-hotplug operations. The
+ * caller can detect other failures by looking at the statistics.
+ */
+bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
+ unsigned long *sum_onl, int *min_onl, int *max_onl)
+{
+ unsigned long delta;
+ int ret;
+ unsigned long starttime;
+
+ if (cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
+ return false;
+
+ if (verbose)
+ pr_alert("%s" TORTURE_FLAG
+ "torture_onoff task: onlining %d\n",
+ torture_type, cpu);
+ starttime = jiffies;
+ (*n_onl_attempts)++;
+ ret = cpu_up(cpu);
+ if (ret) {
+ if (verbose)
+ pr_alert("%s" TORTURE_FLAG
+ "torture_onoff task: online %d failed: errno %d\n",
+ torture_type, cpu, ret);
+ } else {
+ if (verbose)
+ pr_alert("%s" TORTURE_FLAG
+ "torture_onoff task: onlined %d\n",
+ torture_type, cpu);
+ (*n_onl_successes)++;
+ delta = jiffies - starttime;
+ *sum_onl += delta;
+ if (*min_onl < 0) {
+ *min_onl = delta;
+ *max_onl = delta;
+ }
+ if (*min_onl > delta)
+ *min_onl = delta;
+ if (*max_onl < delta)
+ *max_onl = delta;
+ }
+
+ return true;
+}
+EXPORT_SYMBOL_GPL(torture_online);
+
+/*
* Execute random CPU-hotplug operations at the interval specified
* by the onoff_interval.
*/
@@ -89,16 +187,19 @@
torture_onoff(void *arg)
{
int cpu;
- unsigned long delta;
int maxcpu = -1;
DEFINE_TORTURE_RANDOM(rand);
- int ret;
- unsigned long starttime;
VERBOSE_TOROUT_STRING("torture_onoff task started");
for_each_online_cpu(cpu)
maxcpu = cpu;
WARN_ON(maxcpu < 0);
+
+ if (maxcpu == 0) {
+ VERBOSE_TOROUT_STRING("Only one CPU, so CPU-hotplug testing is disabled");
+ goto stop;
+ }
+
if (onoff_holdoff > 0) {
VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
schedule_timeout_interruptible(onoff_holdoff);
@@ -106,69 +207,16 @@
}
while (!torture_must_stop()) {
cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
- if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {
- if (verbose)
- pr_alert("%s" TORTURE_FLAG
- "torture_onoff task: offlining %d\n",
- torture_type, cpu);
- starttime = jiffies;
- n_offline_attempts++;
- ret = cpu_down(cpu);
- if (ret) {
- if (verbose)
- pr_alert("%s" TORTURE_FLAG
- "torture_onoff task: offline %d failed: errno %d\n",
- torture_type, cpu, ret);
- } else {
- if (verbose)
- pr_alert("%s" TORTURE_FLAG
- "torture_onoff task: offlined %d\n",
- torture_type, cpu);
- n_offline_successes++;
- delta = jiffies - starttime;
- sum_offline += delta;
- if (min_offline < 0) {
- min_offline = delta;
- max_offline = delta;
- }
- if (min_offline > delta)
- min_offline = delta;
- if (max_offline < delta)
- max_offline = delta;
- }
- } else if (cpu_is_hotpluggable(cpu)) {
- if (verbose)
- pr_alert("%s" TORTURE_FLAG
- "torture_onoff task: onlining %d\n",
- torture_type, cpu);
- starttime = jiffies;
- n_online_attempts++;
- ret = cpu_up(cpu);
- if (ret) {
- if (verbose)
- pr_alert("%s" TORTURE_FLAG
- "torture_onoff task: online %d failed: errno %d\n",
- torture_type, cpu, ret);
- } else {
- if (verbose)
- pr_alert("%s" TORTURE_FLAG
- "torture_onoff task: onlined %d\n",
- torture_type, cpu);
- n_online_successes++;
- delta = jiffies - starttime;
- sum_online += delta;
- if (min_online < 0) {
- min_online = delta;
- max_online = delta;
- }
- if (min_online > delta)
- min_online = delta;
- if (max_online < delta)
- max_online = delta;
- }
- }
+ if (!torture_offline(cpu,
+ &n_offline_attempts, &n_offline_successes,
+ &sum_offline, &min_offline, &max_offline))
+ torture_online(cpu,
+ &n_online_attempts, &n_online_successes,
+ &sum_online, &min_online, &max_online);
schedule_timeout_interruptible(onoff_interval);
}
+
+stop:
torture_kthread_stopping("torture_onoff");
return 0;
}
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index b9cfdbf..805b704 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1307,22 +1307,6 @@
Say M if you want the RCU performance tests to build as a module.
Say N if you are unsure.
-config RCU_PERF_TEST_RUNNABLE
- bool "performance tests for RCU runnable by default"
- depends on RCU_PERF_TEST = y
- default n
- help
- This option provides a way to build the RCU performance tests
- directly into the kernel without them starting up at boot time.
- You can use /sys/module to manually override this setting.
- This /proc file is available only when the RCU performance
- tests have been built into the kernel.
-
- Say Y here if you want the RCU performance tests to start during
- boot (you probably don't).
- Say N here if you want the RCU performance tests to start only
- after being manually enabled via /sys/module.
-
config RCU_TORTURE_TEST
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
@@ -1340,23 +1324,6 @@
Say M if you want the RCU torture tests to build as a module.
Say N if you are unsure.
-config RCU_TORTURE_TEST_RUNNABLE
- bool "torture tests for RCU runnable by default"
- depends on RCU_TORTURE_TEST = y
- default n
- help
- This option provides a way to build the RCU torture tests
- directly into the kernel without them starting up at boot
- time. You can use /proc/sys/kernel/rcutorture_runnable
- to manually override this setting. This /proc file is
- available only when the RCU torture tests have been built
- into the kernel.
-
- Say Y here if you want the RCU torture tests to start during
- boot (you probably don't).
- Say N here if you want the RCU torture tests to start only
- after being manually enabled via /proc.
-
config RCU_TORTURE_TEST_SLOW_PREINIT
bool "Slow down RCU grace-period pre-initialization to expose races"
depends on RCU_TORTURE_TEST
diff --git a/tools/testing/selftests/rcutorture/bin/functions.sh b/tools/testing/selftests/rcutorture/bin/functions.sh
index b325470..1426a9b 100644
--- a/tools/testing/selftests/rcutorture/bin/functions.sh
+++ b/tools/testing/selftests/rcutorture/bin/functions.sh
@@ -99,8 +99,9 @@
# identify_boot_image qemu-cmd
#
# Returns the relative path to the kernel build image. This will be
-# arch/<arch>/boot/bzImage unless overridden with the TORTURE_BOOT_IMAGE
-# environment variable.
+# arch/<arch>/boot/bzImage or vmlinux if bzImage is not a target for the
+# architecture, unless overridden with the TORTURE_BOOT_IMAGE environment
+# variable.
identify_boot_image () {
if test -n "$TORTURE_BOOT_IMAGE"
then
@@ -110,11 +111,8 @@
qemu-system-x86_64|qemu-system-i386)
echo arch/x86/boot/bzImage
;;
- qemu-system-ppc64)
- echo arch/powerpc/boot/bzImage
- ;;
*)
- echo ""
+ echo vmlinux
;;
esac
fi
@@ -175,7 +173,7 @@
qemu-system-x86_64|qemu-system-i386)
;;
qemu-system-ppc64)
- echo -enable-kvm -M pseries -cpu POWER7 -nodefaults
+ echo -enable-kvm -M pseries -nodefaults
echo -device spapr-vscsi
if test -n "$TORTURE_QEMU_INTERACTIVE" -a -n "$TORTURE_QEMU_MAC"
then
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index 4109f30..ea6e373 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -8,9 +8,9 @@
#
# Usage: kvm-test-1-run.sh config builddir resdir seconds qemu-args boot_args
#
-# qemu-args defaults to "-enable-kvm -soundhw pcspk -nographic", along with
-# arguments specifying the number of CPUs and other
-# options generated from the underlying CPU architecture.
+# qemu-args defaults to "-enable-kvm -nographic", along with arguments
+# specifying the number of CPUs and other options
+# generated from the underlying CPU architecture.
# boot_args defaults to value returned by the per_version_boot_params
# shell function.
#
@@ -96,7 +96,8 @@
then
# Rerunning previous test, so use that test's kernel.
QEMU="`identify_qemu $base_resdir/vmlinux`"
- KERNEL=$base_resdir/bzImage
+ BOOT_IMAGE="`identify_boot_image $QEMU`"
+ KERNEL=$base_resdir/${BOOT_IMAGE##*/} # use the last component of ${BOOT_IMAGE}
ln -s $base_resdir/Make*.out $resdir # for kvm-recheck.sh
ln -s $base_resdir/.config $resdir # for kvm-recheck.sh
elif kvm-build.sh $config_template $builddir $T
@@ -110,7 +111,7 @@
if test -n "$BOOT_IMAGE"
then
cp $builddir/$BOOT_IMAGE $resdir
- KERNEL=$resdir/bzImage
+ KERNEL=$resdir/${BOOT_IMAGE##*/}
else
echo No identifiable boot image, not running KVM, see $resdir.
echo Do the torture scripts know about your architecture?
@@ -147,7 +148,7 @@
fi
# Generate -smp qemu argument.
-qemu_args="-enable-kvm -soundhw pcspk -nographic $qemu_args"
+qemu_args="-enable-kvm -nographic $qemu_args"
cpu_count=`configNR_CPUS.sh $config_template`
cpu_count=`configfrag_boot_cpus "$boot_args" "$config_template" "$cpu_count"`
vcpus=`identify_qemu_vcpus`
@@ -229,6 +230,7 @@
if test $commandcompleted -eq 0 -a -n "$qemu_pid"
then
echo Grace period for qemu job at pid $qemu_pid
+ oldline="`tail $resdir/console.log`"
while :
do
kruntime=`awk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
@@ -238,13 +240,29 @@
else
break
fi
- if test $kruntime -ge $((seconds + $TORTURE_SHUTDOWN_GRACE))
+ must_continue=no
+ newline="`tail $resdir/console.log`"
+ if test "$newline" != "$oldline" && echo $newline | grep -q ' [0-9]\+us : '
+ then
+ must_continue=yes
+ fi
+ last_ts="`tail $resdir/console.log | grep '^\[ *[0-9]\+\.[0-9]\+]' | tail -1 | sed -e 's/^\[ *//' -e 's/\..*$//'`"
+ if test -z "last_ts"
+ then
+ last_ts=0
+ fi
+ if test "$newline" != "$oldline" -a "$last_ts" -lt $((seconds + $TORTURE_SHUTDOWN_GRACE))
+ then
+ must_continue=yes
+ fi
+ if test $must_continue = no -a $kruntime -ge $((seconds + $TORTURE_SHUTDOWN_GRACE))
then
echo "!!! PID $qemu_pid hung at $kruntime vs. $seconds seconds" >> $resdir/Warnings 2>&1
kill -KILL $qemu_pid
break
fi
- sleep 1
+ oldline=$newline
+ sleep 10
done
elif test -z "$qemu_pid"
then
diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index 0d59814..0aed965 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -48,7 +48,7 @@
configs=""
cpus=0
ds=`date +%Y.%m.%d-%H:%M:%S`
-jitter=0
+jitter="-1"
. functions.sh
diff --git a/tools/testing/selftests/rcutorture/bin/parse-console.sh b/tools/testing/selftests/rcutorture/bin/parse-console.sh
index 5eb49b7..08aa7d5 100755
--- a/tools/testing/selftests/rcutorture/bin/parse-console.sh
+++ b/tools/testing/selftests/rcutorture/bin/parse-console.sh
@@ -33,7 +33,7 @@
then
print_warning Console output contains nul bytes, old qemu still running?
fi
-egrep 'Badness|WARNING:|Warn|BUG|===========|Call Trace:|Oops:|detected stalls on CPUs/tasks:|self-detected stall on CPU|Stall ended before state dump start|\?\?\? Writer stall state' < $file | grep -v 'ODEBUG: ' | grep -v 'Warning: unable to open an initial console' > $1.diags
+egrep 'Badness|WARNING:|Warn|BUG|===========|Call Trace:|Oops:|detected stalls on CPUs/tasks:|self-detected stall on CPU|Stall ended before state dump start|\?\?\? Writer stall state|rcu_.*kthread starved for' < $file | grep -v 'ODEBUG: ' | grep -v 'Warning: unable to open an initial console' > $1.diags
if test -s $1.diags
then
print_warning Assertion failure in $file $title
@@ -69,6 +69,11 @@
then
summary="$summary Stalls: $n_stalls"
fi
+ n_starves=`grep -c 'rcu_.*kthread starved for' $1`
+ if test "$n_starves" -ne 0
+ then
+ summary="$summary Starves: $n_starves"
+ fi
print_warning Summary: $summary
else
rm $1.diags
diff --git a/tools/testing/selftests/rcutorture/doc/initrd.txt b/tools/testing/selftests/rcutorture/doc/initrd.txt
index 4170e71..833f826 100644
--- a/tools/testing/selftests/rcutorture/doc/initrd.txt
+++ b/tools/testing/selftests/rcutorture/doc/initrd.txt
@@ -13,6 +13,22 @@
cpio -id < /tmp/initrd.img.zcat
------------------------------------------------------------------------
+Another way to create an initramfs image is using "dracut"[1], which is
+available on many distros, however the initramfs dracut generates is a cpio
+archive with another cpio archive in it, so an extra step is needed to create
+the initrd directory hierarchy.
+
+Here are the commands to create a initrd directory for rcutorture using
+dracut:
+
+------------------------------------------------------------------------
+dracut --no-hostonly --no-hostonly-cmdline --module "base bash shutdown" /tmp/initramfs.img
+cd tools/testing/selftests/rcutorture
+mkdir initrd
+cd initrd
+/usr/lib/dracut/skipcpio /tmp/initramfs.img | zcat | cpio -id < /tmp/initramfs.img
+------------------------------------------------------------------------
+
Interestingly enough, if you are running rcutorture, you don't really
need userspace in many cases. Running without userspace has the
advantage of allowing you to test your kernel independently of the
@@ -89,3 +105,9 @@
do
sleep 10
done
+------------------------------------------------------------------------
+
+References:
+[1]: https://dracut.wiki.kernel.org/index.php/Main_Page
+[2]: http://blog.elastocloud.org/2015/06/rapid-linux-kernel-devtest-with-qemu.html
+[3]: https://www.centos.org/forums/viewtopic.php?t=51621
