10bde81c74
The wakeup in preemptive (wip) monitor verifies if the
wakeup events always take place with preemption disabled:
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v
#==================#
H preemptive H <+
#==================# |
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| preempt_disable | preempt_enable
v |
sched_waking +------------------+ |
+--------------- | | |
| | non_preemptive | |
+--------------> | | -+
+------------------+
The wakeup event always takes place with preemption disabled because
of the scheduler synchronization. However, because the preempt_count
and its trace event are not atomic with regard to interrupts, some
inconsistencies might happen.
The documentation illustrates one of these cases.
Link: https://lkml.kernel.org/r/c98ca678df81115fddc04921b3c79720c836b18f.1659052063.git.bristot@kernel.org
Cc: Wim Van Sebroeck <wim@linux-watchdog.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Gabriele Paoloni <gpaoloni@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Tao Zhou <tao.zhou@linux.dev>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
89 lines
2.0 KiB
C
89 lines
2.0 KiB
C
// 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 "wip"
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#include <trace/events/rv.h>
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#include <trace/events/sched.h>
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#include <trace/events/preemptirq.h>
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#include "wip.h"
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struct rv_monitor rv_wip;
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DECLARE_DA_MON_PER_CPU(wip, unsigned char);
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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_wip(preempt_disable_wip);
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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_start_event_wip(preempt_enable_wip);
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}
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static void handle_sched_waking(void *data, struct task_struct *task)
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{
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da_handle_event_wip(sched_waking_wip);
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}
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static int enable_wip(void)
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{
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int retval;
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retval = da_monitor_init_wip();
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if (retval)
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return retval;
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rv_attach_trace_probe("wip", preempt_enable, handle_preempt_enable);
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rv_attach_trace_probe("wip", sched_waking, handle_sched_waking);
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rv_attach_trace_probe("wip", preempt_disable, handle_preempt_disable);
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return 0;
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}
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static void disable_wip(void)
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{
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rv_wip.enabled = 0;
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rv_detach_trace_probe("wip", preempt_disable, handle_preempt_disable);
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rv_detach_trace_probe("wip", preempt_enable, handle_preempt_enable);
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rv_detach_trace_probe("wip", sched_waking, handle_sched_waking);
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da_monitor_destroy_wip();
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}
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struct rv_monitor rv_wip = {
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.name = "wip",
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.description = "wakeup in preemptive per-cpu testing monitor.",
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.enable = enable_wip,
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.disable = disable_wip,
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.reset = da_monitor_reset_all_wip,
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.enabled = 0,
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};
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static int register_wip(void)
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{
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rv_register_monitor(&rv_wip);
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return 0;
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}
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static void unregister_wip(void)
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{
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rv_unregister_monitor(&rv_wip);
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}
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module_init(register_wip);
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module_exit(unregister_wip);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Daniel Bristot de Oliveira <bristot@kernel.org>");
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MODULE_DESCRIPTION("wip: wakeup in preemptive - per-cpu sample monitor.");
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