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rv: Add opid per-cpu monitor
Add a per-cpu monitor as part of the sched model: * opid: operations with preemption and irq disabled Monitor to ensure wakeup and need_resched occur with irq and preemption disabled or in irq handlers. Cc: Jonathan Corbet <[email protected]> Cc: Masami Hiramatsu <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Tomas Glozar <[email protected]> Cc: Juri Lelli <[email protected]> Cc: Clark Williams <[email protected]> Cc: John Kacur <[email protected]> Link: https://lore.kernel.org/[email protected] Signed-off-by: Gabriele Monaco <[email protected]> Acked-by: Nam Cao <[email protected]> Tested-by: Nam Cao <[email protected]> Signed-off-by: Steven Rostedt (Google) <[email protected]>
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‎Documentation/trace/rv/monitor_sched.rst‎

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@@ -341,6 +341,61 @@ can be triggered also by preemption, but cannot occur after the task got to
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| | switch_yield
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+-----------+ wakeup
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Monitor opid
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------------
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The operations with preemption and irq disabled (opid) monitor ensures
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operations like ``wakeup`` and ``need_resched`` occur with interrupts and
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preemption disabled or during interrupt context, in such case preemption may
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not be disabled explicitly.
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``need_resched`` can be set by some RCU internals functions, in which case it
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doesn't match a task wakeup and might occur with only interrupts disabled::
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| sched_need_resched
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| sched_waking
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| irq_entry
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| +--------------------+
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v v |
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+------------------------------------------------------+
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+----------- | disabled | <+
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| +------------------------------------------------------+ |
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| | ^ |
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| | preempt_disable sched_need_resched |
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| preempt_enable | +--------------------+ |
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| v | v | |
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| +------------------------------------------------------+ |
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| | irq_disabled | |
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| +------------------------------------------------------+ |
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| | | ^ |
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| irq_entry irq_entry | | |
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| sched_need_resched v | irq_disable |
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| sched_waking +--------------+ | | |
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| +----- | | irq_enable | |
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| | | in_irq | | | |
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| +----> | | | | |
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| +--------------+ | | irq_disable
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| | | | |
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| irq_enable | irq_enable | | |
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| v v | |
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| #======================================================# |
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| H enabled H |
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| #======================================================# |
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| | ^ ^ preempt_enable | |
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| preempt_disable preempt_enable +--------------------+ |
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| v | |
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| +------------------+ | |
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+----------> | preempt_disabled | -+ |
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+------------------+ |
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| |
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+-------------------------------------------------------+
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This monitor is designed to work on ``PREEMPT_RT`` kernels, the special case of
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events occurring in interrupt context is a shortcut to identify valid scenarios
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where the preemption tracepoints might not be visible, during interrupts
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preemption is always disabled. On non- ``PREEMPT_RT`` kernels, the interrupts
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might invoke a softirq to set ``need_resched`` and wake up a task. This is
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another special case that is currently not supported by the monitor.
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References
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----------
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‎kernel/trace/rv/Kconfig‎

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@@ -57,6 +57,7 @@ source "kernel/trace/rv/monitors/snep/Kconfig"
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source "kernel/trace/rv/monitors/sts/Kconfig"
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source "kernel/trace/rv/monitors/nrp/Kconfig"
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source "kernel/trace/rv/monitors/sssw/Kconfig"
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source "kernel/trace/rv/monitors/opid/Kconfig"
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# Add new sched monitors here
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source "kernel/trace/rv/monitors/rtapp/Kconfig"

‎kernel/trace/rv/Makefile‎

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@@ -16,6 +16,7 @@ obj-$(CONFIG_RV_MON_SLEEP) += monitors/sleep/sleep.o
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obj-$(CONFIG_RV_MON_STS) += monitors/sts/sts.o
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obj-$(CONFIG_RV_MON_NRP) += monitors/nrp/nrp.o
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obj-$(CONFIG_RV_MON_SSSW) += monitors/sssw/sssw.o
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obj-$(CONFIG_RV_MON_OPID) += monitors/opid/opid.o
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# Add new monitors here
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obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
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obj-$(CONFIG_RV_REACT_PRINTK) += reactor_printk.o

‎kernel/trace/rv/monitors/opid/Kconfig‎

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# SPDX-License-Identifier: GPL-2.0-only
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#
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config RV_MON_OPID
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depends on RV
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depends on TRACE_IRQFLAGS
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depends on TRACE_PREEMPT_TOGGLE
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depends on RV_MON_SCHED
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default y if PREEMPT_RT
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select DA_MON_EVENTS_IMPLICIT
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bool "opid monitor"
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help
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Monitor to ensure operations like wakeup and need resched occur with
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interrupts and preemption disabled or during IRQs, where preemption
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may not be disabled explicitly.
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This monitor is unstable on !PREEMPT_RT, say N unless you are testing it.
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For further information, see:
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Documentation/trace/rv/monitor_sched.rst

‎kernel/trace/rv/monitors/opid/opid.c‎

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// SPDX-License-Identifier: GPL-2.0
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#include <linux/ftrace.h>
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#include <linux/tracepoint.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/rv.h>
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#include <rv/instrumentation.h>
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#include <rv/da_monitor.h>
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#define MODULE_NAME "opid"
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#include <trace/events/sched.h>
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#include <trace/events/irq.h>
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#include <trace/events/preemptirq.h>
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#include <rv_trace.h>
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#include <monitors/sched/sched.h>
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#include "opid.h"
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static struct rv_monitor rv_opid;
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DECLARE_DA_MON_PER_CPU(opid, unsigned char);
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#ifdef CONFIG_X86_LOCAL_APIC
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#include <asm/trace/irq_vectors.h>
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static void handle_vector_irq_entry(void *data, int vector)
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{
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da_handle_event_opid(irq_entry_opid);
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}
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static void attach_vector_irq(void)
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{
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rv_attach_trace_probe("opid", local_timer_entry, handle_vector_irq_entry);
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if (IS_ENABLED(CONFIG_IRQ_WORK))
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rv_attach_trace_probe("opid", irq_work_entry, handle_vector_irq_entry);
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if (IS_ENABLED(CONFIG_SMP)) {
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rv_attach_trace_probe("opid", reschedule_entry, handle_vector_irq_entry);
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rv_attach_trace_probe("opid", call_function_entry, handle_vector_irq_entry);
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rv_attach_trace_probe("opid", call_function_single_entry, handle_vector_irq_entry);
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}
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}
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static void detach_vector_irq(void)
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{
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rv_detach_trace_probe("opid", local_timer_entry, handle_vector_irq_entry);
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if (IS_ENABLED(CONFIG_IRQ_WORK))
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rv_detach_trace_probe("opid", irq_work_entry, handle_vector_irq_entry);
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if (IS_ENABLED(CONFIG_SMP)) {
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rv_detach_trace_probe("opid", reschedule_entry, handle_vector_irq_entry);
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rv_detach_trace_probe("opid", call_function_entry, handle_vector_irq_entry);
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rv_detach_trace_probe("opid", call_function_single_entry, handle_vector_irq_entry);
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}
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}
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#else
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/* We assume irq_entry tracepoints are sufficient on other architectures */
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static void attach_vector_irq(void) { }
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static void detach_vector_irq(void) { }
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#endif
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static void handle_irq_disable(void *data, unsigned long ip, unsigned long parent_ip)
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{
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da_handle_event_opid(irq_disable_opid);
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}
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static void handle_irq_enable(void *data, unsigned long ip, unsigned long parent_ip)
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{
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da_handle_event_opid(irq_enable_opid);
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}
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static void handle_irq_entry(void *data, int irq, struct irqaction *action)
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{
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da_handle_event_opid(irq_entry_opid);
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}
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static void handle_preempt_disable(void *data, unsigned long ip, unsigned long parent_ip)
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{
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da_handle_event_opid(preempt_disable_opid);
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}
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static void handle_preempt_enable(void *data, unsigned long ip, unsigned long parent_ip)
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{
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da_handle_event_opid(preempt_enable_opid);
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}
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static void handle_sched_need_resched(void *data, struct task_struct *tsk, int cpu, int tif)
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{
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/* The monitor's intitial state is not in_irq */
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if (this_cpu_read(hardirq_context))
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da_handle_event_opid(sched_need_resched_opid);
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else
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da_handle_start_event_opid(sched_need_resched_opid);
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}
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static void handle_sched_waking(void *data, struct task_struct *p)
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{
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/* The monitor's intitial state is not in_irq */
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if (this_cpu_read(hardirq_context))
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da_handle_event_opid(sched_waking_opid);
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else
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da_handle_start_event_opid(sched_waking_opid);
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}
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static int enable_opid(void)
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{
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int retval;
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retval = da_monitor_init_opid();
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if (retval)
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return retval;
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rv_attach_trace_probe("opid", irq_disable, handle_irq_disable);
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rv_attach_trace_probe("opid", irq_enable, handle_irq_enable);
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rv_attach_trace_probe("opid", irq_handler_entry, handle_irq_entry);
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rv_attach_trace_probe("opid", preempt_disable, handle_preempt_disable);
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rv_attach_trace_probe("opid", preempt_enable, handle_preempt_enable);
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rv_attach_trace_probe("opid", sched_set_need_resched_tp, handle_sched_need_resched);
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rv_attach_trace_probe("opid", sched_waking, handle_sched_waking);
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attach_vector_irq();
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return 0;
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}
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static void disable_opid(void)
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{
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rv_opid.enabled = 0;
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rv_detach_trace_probe("opid", irq_disable, handle_irq_disable);
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rv_detach_trace_probe("opid", irq_enable, handle_irq_enable);
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rv_detach_trace_probe("opid", irq_handler_entry, handle_irq_entry);
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rv_detach_trace_probe("opid", preempt_disable, handle_preempt_disable);
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rv_detach_trace_probe("opid", preempt_enable, handle_preempt_enable);
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rv_detach_trace_probe("opid", sched_set_need_resched_tp, handle_sched_need_resched);
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rv_detach_trace_probe("opid", sched_waking, handle_sched_waking);
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detach_vector_irq();
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da_monitor_destroy_opid();
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}
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/*
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* This is the monitor register section.
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*/
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static struct rv_monitor rv_opid = {
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.name = "opid",
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.description = "operations with preemption and irq disabled.",
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.enable = enable_opid,
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.disable = disable_opid,
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.reset = da_monitor_reset_all_opid,
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.enabled = 0,
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};
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static int __init register_opid(void)
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{
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return rv_register_monitor(&rv_opid, &rv_sched);
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}
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static void __exit unregister_opid(void)
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{
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rv_unregister_monitor(&rv_opid);
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}
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module_init(register_opid);
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module_exit(unregister_opid);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Gabriele Monaco <[email protected]>");
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MODULE_DESCRIPTION("opid: operations with preemption and irq disabled.");

‎kernel/trace/rv/monitors/opid/opid.h‎

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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Automatically generated C representation of opid automaton
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* For further information about this format, see kernel documentation:
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* Documentation/trace/rv/deterministic_automata.rst
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*/
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enum states_opid {
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disabled_opid = 0,
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enabled_opid,
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in_irq_opid,
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irq_disabled_opid,
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preempt_disabled_opid,
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state_max_opid
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};
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#define INVALID_STATE state_max_opid
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enum events_opid {
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irq_disable_opid = 0,
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irq_enable_opid,
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irq_entry_opid,
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preempt_disable_opid,
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preempt_enable_opid,
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sched_need_resched_opid,
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sched_waking_opid,
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event_max_opid
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};
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struct automaton_opid {
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char *state_names[state_max_opid];
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char *event_names[event_max_opid];
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unsigned char function[state_max_opid][event_max_opid];
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unsigned char initial_state;
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bool final_states[state_max_opid];
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};
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static const struct automaton_opid automaton_opid = {
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.state_names = {
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"disabled",
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"enabled",
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"in_irq",
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"irq_disabled",
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"preempt_disabled"
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},
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.event_names = {
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"irq_disable",
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"irq_enable",
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"irq_entry",
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"preempt_disable",
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"preempt_enable",
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"sched_need_resched",
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"sched_waking"
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},
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.function = {
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{
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INVALID_STATE,
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preempt_disabled_opid,
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disabled_opid,
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INVALID_STATE,
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irq_disabled_opid,
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disabled_opid,
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disabled_opid
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},
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{
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irq_disabled_opid,
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INVALID_STATE,
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INVALID_STATE,
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preempt_disabled_opid,
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enabled_opid,
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INVALID_STATE,
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INVALID_STATE
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},
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{
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INVALID_STATE,
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enabled_opid,
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in_irq_opid,
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INVALID_STATE,
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INVALID_STATE,
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in_irq_opid,
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in_irq_opid
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},
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{
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INVALID_STATE,
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enabled_opid,
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in_irq_opid,
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disabled_opid,
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INVALID_STATE,
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irq_disabled_opid,
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INVALID_STATE
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},
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{
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disabled_opid,
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INVALID_STATE,
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INVALID_STATE,
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INVALID_STATE,
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enabled_opid,
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INVALID_STATE,
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INVALID_STATE
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},
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},
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.initial_state = disabled_opid,
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.final_states = { 0, 1, 0, 0, 0 },
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};

‎kernel/trace/rv/monitors/opid/opid_trace.h‎

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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Snippet to be included in rv_trace.h
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*/
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#ifdef CONFIG_RV_MON_OPID
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DEFINE_EVENT(event_da_monitor, event_opid,
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TP_PROTO(char *state, char *event, char *next_state, bool final_state),
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TP_ARGS(state, event, next_state, final_state));
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DEFINE_EVENT(error_da_monitor, error_opid,
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TP_PROTO(char *state, char *event),
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TP_ARGS(state, event));
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#endif /* CONFIG_RV_MON_OPID */

‎kernel/trace/rv/rv_trace.h‎

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#include <monitors/scpd/scpd_trace.h>
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#include <monitors/snep/snep_trace.h>
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#include <monitors/sts/sts_trace.h>
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#include <monitors/opid/opid_trace.h>
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// Add new monitors based on CONFIG_DA_MON_EVENTS_IMPLICIT here
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#endif /* CONFIG_DA_MON_EVENTS_IMPLICIT */

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