On Tue, May 28, 2019 at 05:16:22PM +0200, Daniel Bristot de Oliveira wrote:
> prempt_disable/enable tracepoints occurs only in the preemption
> enabled <-> disable transition. As preempt_latency_stop() and
> preempt_latency_start() already do this control, avoid code
> duplication by using these functions in the softirq code as well.
>
> RFC: Should we move preempt_latency_start/preempt_latency_stop
> to a trace source file... or even a header?
Yes, I think so. Also this patch changes CALLER_ADDR0 passed to the
tracepoint because there's one more level of a non-inlined function call
in the call chain right? Very least the changelog should document this
change in functional behavior, IMO.
Looks like a nice change otherwise, thanks!
> Signed-off-by: Daniel Bristot de Oliveira <bris...@redhat.com>
> Cc: "Steven Rostedt (VMware)" <rost...@goodmis.org>
> Cc: Ingo Molnar <mi...@redhat.com>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
> Cc: Matthias Kaehlcke <m...@chromium.org>
> Cc: "Joel Fernandes (Google)" <j...@joelfernandes.org>
> Cc: Frederic Weisbecker <frede...@kernel.org>
> Cc: Yangtao Li <tiny.win...@gmail.com>
> Cc: Tommaso Cucinotta <tommaso.cucino...@santannapisa.it>
> Cc: linux-kernel@vger.kernel.org
> ---
> kernel/sched/core.c | 4 ++--
> kernel/softirq.c | 13 +++++--------
> 2 files changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 874c427742a9..8c0b414e45dc 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3152,7 +3152,7 @@ static inline void sched_tick_stop(int cpu) { }
> * If the value passed in is equal to the current preempt count
> * then we just disabled preemption. Start timing the latency.
> */
> -static inline void preempt_latency_start(int val)
> +void preempt_latency_start(int val)
> {
> if (preempt_count() == val) {
> unsigned long ip = get_lock_parent_ip();
> @@ -3189,7 +3189,7 @@ NOKPROBE_SYMBOL(preempt_count_add);
> * If the value passed in equals to the current preempt count
> * then we just enabled preemption. Stop timing the latency.
> */
> -static inline void preempt_latency_stop(int val)
> +void preempt_latency_stop(int val)
> {
> if (preempt_count() == val)
> trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 2c3382378d94..c9ad89c3dfed 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -108,6 +108,8 @@ static bool ksoftirqd_running(unsigned long pending)
> * where hardirqs are disabled legitimately:
> */
> #ifdef CONFIG_TRACE_IRQFLAGS
> +extern void preempt_latency_start(int val);
> +extern void preempt_latency_stop(int val);
> void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
> {
> unsigned long flags;
> @@ -130,12 +132,8 @@ void __local_bh_disable_ip(unsigned long ip, unsigned
> int cnt)
> trace_softirqs_off(ip);
> raw_local_irq_restore(flags);
>
> - if (preempt_count() == cnt) {
> -#ifdef CONFIG_DEBUG_PREEMPT
> - current->preempt_disable_ip = get_lock_parent_ip();
> -#endif
> - trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
> - }
> + preempt_latency_start(cnt);
> +
> }
> EXPORT_SYMBOL(__local_bh_disable_ip);
> #endif /* CONFIG_TRACE_IRQFLAGS */
> @@ -144,8 +142,7 @@ static void __local_bh_enable(unsigned int cnt)
> {
> lockdep_assert_irqs_disabled();
>
> - if (preempt_count() == cnt)
> - trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
> + preempt_latency_stop(cnt);
>
> if (softirq_count() == (cnt & SOFTIRQ_MASK))
> trace_softirqs_on(_RET_IP_);
> --
> 2.20.1
>
