linux-kernel - Re: [PATCH] torture: use ktime

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Message-Id: <20160620182105.GV3923@linux.vnet.ibm.com>
Date:	Mon, 20 Jun 2016 11:21:05 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Boqun Feng <boqun.feng@...il.com>,
	Josh Triplett <josh@...htriplett.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] torture: use ktime_t consistently

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@...db.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@...ux.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@...ux.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);
 	}