Re: [PATCH] torture: use ktime_t consistently

Paul E. McKenney
2016-06-20T18:21:19Z

On Mon, Jun 20, 2016 at 05:56:40PM +0200, Arnd Bergmann wrote:
> A recent change accidentally introduced a 64-bit division in torture_shutdown,
> which fails to build on 32-bit architectures:
>
> kernel/built-in.o: In function `torture_shutdown':
> :(.text+0x4b29a): undefined reference to `__aeabi_uldivmod'
>
> This converts the function to use ktime_t instead, which also simplifies
> it a little.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: b4aa201e0c7c ("torture: Convert torture_shutdown() to hrtimer")

Thank you, Arnd!

I ended up squashing in the alternative change below before I saw your
email address. This is currently untested, so I might well end up using
yours instead should breakage ensue. Given that I haven't done much
with ktime_t, breakage is rather likely.

Thoughts?

Thanx, Paul

------------------------------------------------------------------------

commit 303c4c9474e84112ab2474cd383282f5dbfc75c3
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Sat Jun 18 07:45:43 2016 -0700

torture: Convert torture_shutdown() to hrtimer

Upcoming changes to the timer wheel introduce significant inaccuracy
and possibly also an ultimate limit on timeout duration. This is
a problem for the current implementation of torture_shutdown() because
(1) shutdown times are user-specified, and can therefore be quite
long, and (2) the torture scripting will kill a test instance that
runs for more than a few minutes longer than scheduled. This commit
therefore converts the torture_shutdown() timed waits to an hrtimer.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/torture.c b/kernel/torture.c
index 75961b3decfe..1c1b5960d27f 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -43,6 +43,7 @@
#include <linux/stat.h>
#include <linux/slab.h>
#include <linux/trace_clock.h>
+#include <linux/ktime.h>
#include <asm/byteorder.h>
#include <linux/torture.h>

@@ -446,9 +447,9 @@ EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);
* Variables for auto-shutdown. This allows "lights out" torture runs
* to be fully scripted.
*/
-static int shutdown_secs; /* desired test duration in seconds. */
+static ktime_t shutdown_ms; /* desired test duration in seconds. */
static struct task_struct *shutdown_task;
-static unsigned long shutdown_time; /* jiffies to system shutdown. */
+static ktime_t shutdown_time; /* jiffies to system shutdown. */
static void (*torture_shutdown_hook)(void);

/*
@@ -471,20 +472,21 @@ EXPORT_SYMBOL_GPL(torture_shutdown_absorb);
*/
static int torture_shutdown(void *arg)
{
- long delta;
- unsigned long jiffies_snap;
+ ktime_t delta;
+ ktime_t ktime_snap;

VERBOSE_TOROUT_STRING("torture_shutdown task started");
- jiffies_snap = jiffies;
- while (ULONG_CMP_LT(jiffies_snap, shutdown_time) &&
+ ktime_snap = ktime_get();
+ while (ktime_before(ktime_snap, shutdown_time) &&
!torture_must_stop()) {
- delta = shutdown_time - jiffies_snap;
+ delta = ktime_sub(shutdown_time, ktime_snap);
if (verbose)
pr_alert("%s" TORTURE_FLAG
- "torture_shutdown task: %lu jiffies remaining\n",
- torture_type, delta);
- schedule_timeout_interruptible(delta);
- jiffies_snap = jiffies;
+ "torture_shutdown task: %llu ms remaining\n",
+ torture_type, ktime_to_ms(delta));
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_hrtimeout(&delta, HRTIMER_MODE_REL);
+ ktime_snap = ktime_get();
}
if (torture_must_stop()) {
torture_kthread_stopping("torture_shutdown");
@@ -511,10 +513,10 @@ int torture_shutdown_init(int ssecs, void (*cleanup)(void))
{
int ret = 0;

- shutdown_secs = ssecs;
torture_shutdown_hook = cleanup;
- if (shutdown_secs > 0) {
- shutdown_time = jiffies + shutdown_secs * HZ;
+ if (ssecs > 0) {
+ shutdown_ms = ms_to_ktime(ssecs * 1000ULL);
+ shutdown_time = ktime_add(ktime_get(), shutdown_ms);
ret = torture_create_kthread(torture_shutdown, NULL,
shutdown_task);
}