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Message-ID: <20250307123849.1e5d7543@gandalf.local.home>
Date: Fri, 7 Mar 2025 12:38:49 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Gabriele Monaco <gmonaco@...hat.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, Peter
Zijlstra <peterz@...radead.org>, Masami Hiramatsu <mhiramat@...nel.org>,
linux-trace-kernel@...r.kernel.org, Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH v5 1/9] sched: Add sched tracepoints for RV task model
Can I get an Acked-by from one of the scheduler maintainers?
-- Steve
On Wed, 5 Mar 2025 15:03:54 +0100
Gabriele Monaco <gmonaco@...hat.com> wrote:
> Add the following tracepoints:
> * sched_entry(bool preempt, ip)
> Called while entering __schedule
> * sched_exit(bool is_switch, ip)
> Called while exiting __schedule
> * sched_set_state(task, curr_state, state)
> Called when a task changes its state (to and from running)
>
> These tracepoints are useful to describe the Linux task model and are
> adapted from the patches by Daniel Bristot de Oliveira
> (https://bristot.me/linux-task-model/).
>
> Signed-off-by: Gabriele Monaco <gmonaco@...hat.com>
> ---
> include/linux/rv.h | 2 +-
> include/linux/sched.h | 16 ++++++++++++++++
> include/trace/events/sched.h | 13 +++++++++++++
> kernel/sched/core.c | 23 ++++++++++++++++++++++-
> tools/verification/rv/include/rv.h | 2 +-
> 5 files changed, 53 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/rv.h b/include/linux/rv.h
> index 8883b41d88ec4..55d458be53a4c 100644
> --- a/include/linux/rv.h
> +++ b/include/linux/rv.h
> @@ -7,7 +7,7 @@
> #ifndef _LINUX_RV_H
> #define _LINUX_RV_H
>
> -#define MAX_DA_NAME_LEN 24
> +#define MAX_DA_NAME_LEN 32
>
> #ifdef CONFIG_RV
> /*
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 9632e3318e0d6..45a61a0b97903 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -46,6 +46,7 @@
> #include <linux/rv.h>
> #include <linux/livepatch_sched.h>
> #include <linux/uidgid_types.h>
> +#include <linux/tracepoint-defs.h>
> #include <asm/kmap_size.h>
>
> /* task_struct member predeclarations (sorted alphabetically): */
> @@ -186,6 +187,12 @@ struct user_event_mm;
> # define debug_rtlock_wait_restore_state() do { } while (0)
> #endif
>
> +#define trace_set_current_state(state_value) \
> + do { \
> + if (tracepoint_enabled(sched_set_state_tp)) \
> + __trace_set_current_state(state_value); \
> + } while (0)
> +
> /*
> * set_current_state() includes a barrier so that the write of current->__state
> * is correctly serialised wrt the caller's subsequent test of whether to
> @@ -226,12 +233,14 @@ struct user_event_mm;
> #define __set_current_state(state_value) \
> do { \
> debug_normal_state_change((state_value)); \
> + trace_set_current_state(state_value); \
> WRITE_ONCE(current->__state, (state_value)); \
> } while (0)
>
> #define set_current_state(state_value) \
> do { \
> debug_normal_state_change((state_value)); \
> + trace_set_current_state(state_value); \
> smp_store_mb(current->__state, (state_value)); \
> } while (0)
>
> @@ -247,6 +256,7 @@ struct user_event_mm;
> \
> raw_spin_lock_irqsave(¤t->pi_lock, flags); \
> debug_special_state_change((state_value)); \
> + trace_set_current_state(state_value); \
> WRITE_ONCE(current->__state, (state_value)); \
> raw_spin_unlock_irqrestore(¤t->pi_lock, flags); \
> } while (0)
> @@ -282,6 +292,7 @@ struct user_event_mm;
> raw_spin_lock(¤t->pi_lock); \
> current->saved_state = current->__state; \
> debug_rtlock_wait_set_state(); \
> + trace_set_current_state(TASK_RTLOCK_WAIT); \
> WRITE_ONCE(current->__state, TASK_RTLOCK_WAIT); \
> raw_spin_unlock(¤t->pi_lock); \
> } while (0);
> @@ -291,6 +302,7 @@ struct user_event_mm;
> lockdep_assert_irqs_disabled(); \
> raw_spin_lock(¤t->pi_lock); \
> debug_rtlock_wait_restore_state(); \
> + trace_set_current_state(current->saved_state); \
> WRITE_ONCE(current->__state, current->saved_state); \
> current->saved_state = TASK_RUNNING; \
> raw_spin_unlock(¤t->pi_lock); \
> @@ -327,6 +339,10 @@ extern void io_schedule_finish(int token);
> extern long io_schedule_timeout(long timeout);
> extern void io_schedule(void);
>
> +/* wrapper function to trace from this header file */
> +DECLARE_TRACEPOINT(sched_set_state_tp);
> +extern void __trace_set_current_state(int state_value);
> +
> /**
> * struct prev_cputime - snapshot of system and user cputime
> * @utime: time spent in user mode
> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index 9ea4c404bd4ef..90545125c9031 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -824,6 +824,19 @@ DECLARE_TRACE(sched_compute_energy_tp,
> unsigned long max_util, unsigned long busy_time),
> TP_ARGS(p, dst_cpu, energy, max_util, busy_time));
>
> +DECLARE_TRACE(sched_entry_tp,
> + TP_PROTO(bool preempt, unsigned long ip),
> + TP_ARGS(preempt, ip));
> +
> +DECLARE_TRACE(sched_exit_tp,
> + TP_PROTO(bool is_switch, unsigned long ip),
> + TP_ARGS(is_switch, ip));
> +
> +DECLARE_TRACE_CONDITION(sched_set_state_tp,
> + TP_PROTO(struct task_struct *tsk, int state),
> + TP_ARGS(tsk, state),
> + TP_CONDITION(!!(tsk->__state) != !!state));
> +
> #endif /* _TRACE_SCHED_H */
>
> /* This part must be outside protection */
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 67189907214d3..5d36ccf565e94 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -491,6 +491,16 @@ sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { }
>
> #endif /* CONFIG_SCHED_CORE */
>
> +/* need a wrapper since we may need to trace from modules */
> +EXPORT_TRACEPOINT_SYMBOL(sched_set_state_tp);
> +
> +/* Call via the helper macro trace_set_current_state. */
> +void __trace_set_current_state(int state_value)
> +{
> + trace_sched_set_state_tp(current, state_value);
> +}
> +EXPORT_SYMBOL(__trace_set_current_state);
> +
> /*
> * Serialization rules:
> *
> @@ -5307,6 +5317,12 @@ asmlinkage __visible void schedule_tail(struct task_struct *prev)
> */
>
> finish_task_switch(prev);
> + /*
> + * This is a special case: the newly created task has just
> + * switched the context for the first time. It is returning from
> + * schedule for the first time in this path.
> + */
> + trace_sched_exit_tp(true, CALLER_ADDR0);
> preempt_enable();
>
> if (current->set_child_tid)
> @@ -6650,12 +6666,15 @@ static void __sched notrace __schedule(int sched_mode)
> * as a preemption by schedule_debug() and RCU.
> */
> bool preempt = sched_mode > SM_NONE;
> + bool is_switch = false;
> unsigned long *switch_count;
> unsigned long prev_state;
> struct rq_flags rf;
> struct rq *rq;
> int cpu;
>
> + trace_sched_entry_tp(preempt, CALLER_ADDR0);
> +
> cpu = smp_processor_id();
> rq = cpu_rq(cpu);
> prev = rq->curr;
> @@ -6723,7 +6742,8 @@ static void __sched notrace __schedule(int sched_mode)
> rq->last_seen_need_resched_ns = 0;
> #endif
>
> - if (likely(prev != next)) {
> + is_switch = prev != next;
> + if (likely(is_switch)) {
> rq->nr_switches++;
> /*
> * RCU users of rcu_dereference(rq->curr) may not see
> @@ -6768,6 +6788,7 @@ static void __sched notrace __schedule(int sched_mode)
> __balance_callbacks(rq);
> raw_spin_rq_unlock_irq(rq);
> }
> + trace_sched_exit_tp(is_switch, CALLER_ADDR0);
> }
>
> void __noreturn do_task_dead(void)
> diff --git a/tools/verification/rv/include/rv.h b/tools/verification/rv/include/rv.h
> index 770fd6da36107..0cab1037a98f7 100644
> --- a/tools/verification/rv/include/rv.h
> +++ b/tools/verification/rv/include/rv.h
> @@ -1,7 +1,7 @@
> // SPDX-License-Identifier: GPL-2.0
>
> #define MAX_DESCRIPTION 1024
> -#define MAX_DA_NAME_LEN 24
> +#define MAX_DA_NAME_LEN 32
>
> struct monitor {
> char name[MAX_DA_NAME_LEN];
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