On Mon, Jun 18, 2018 at 04:47:34PM +0200, Arnd Bergmann wrote:
> The get_seconds() call is deprecated because it overflows on 32-bit
> architectures. The algorithm in rcu_torture_stall() can deal with
> the overflow, but another problem here is that using a CLOCK_REALTIME
> stamp can lead to a false-positive stall warning when a settimeofday()
> happens concurrently.
>
> Using ktime_get_seconds() instead avoids those issues and will never
> overflow. The added cast to 'unsigned long' however is necessary to
> make ULONG_CMP_LT() work correctly.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
Queued for testing and review, thank you! If things go well, I
expect this to be ready for the v4.19 merge window.
Thanx, Paul
> ---
> kernel/rcu/rcutorture.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index 42fcb7f05fac..f42cf69ef539 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -1446,7 +1446,7 @@ static int rcu_torture_stall(void *args)
> VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
> }
> if (!kthread_should_stop()) {
> - stop_at = get_seconds() + stall_cpu;
> + stop_at = ktime_get_seconds() + stall_cpu;
> /* RCU CPU stall is expected behavior in following code. */
> rcu_read_lock();
> if (stall_cpu_irqsoff)
> @@ -1455,7 +1455,8 @@ static int rcu_torture_stall(void *args)
> preempt_disable();
> pr_alert("rcu_torture_stall start on CPU %d.\n",
> smp_processor_id());
> - while (ULONG_CMP_LT(get_seconds(), stop_at))
> + while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
> + stop_at))
> continue; /* Induce RCU CPU stall warning. */
> if (stall_cpu_irqsoff)
> local_irq_enable();
> --
> 2.9.0
>
