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rv/monitor: Add the wip monitor 

The wakeup in preemptive (wip) monitor verifies if the
wakeup events always take place with preemption disabled:

                     |
                     |
                     v
                   #==================#
                   H    preemptive    H <+
                   #==================#  |
                     |                   |
                     | 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>
This commit is contained in:
Daniel Bristot de Oliveira 2022-07-29 11:38:52 +02:00 committed by Steven Rostedt (Google)
parent 8812d21219
commit 10bde81c74
7 changed files with 111 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Documentation/trace/rv/index.rst
View File

@ -10,3 +10,4 @@ Runtime Verification
deterministic_automata.rst
da_monitor_synthesis.rst
da_monitor_instrumentation.rst
monitor_wip.rst

55
Documentation/trace/rv/monitor_wip.rst Normal file
View File

@ -0,0 +1,55 @@
Monitor wip
===========
- Name: wip - wakeup in preemptive
- Type: per-cpu deterministic automaton
- Author: Daniel Bristot de Oliveira <bristot@kernel.org>
Description
-----------
The wakeup in preemptive (wip) monitor is a sample per-cpu monitor
that verifies if the wakeup events always take place with
preemption disabled::
|
|
v
#==================#
H preemptive H <+
#==================# |
| |
| 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. For example::
preempt_disable() {
__preempt_count_add(1)
-------> smp_apic_timer_interrupt() {
preempt_disable()
do not trace (preempt count >= 1)
wake up a thread
preempt_enable()
do not trace (preempt count >= 1)
}
<------
trace_preempt_disable();
}
This problem was reported and discussed here:
https://lore.kernel.org/r/cover.1559051152.git.bristot@redhat.com/
Specification
-------------
Grapviz Dot file in tools/verification/models/wip.dot

10
include/trace/events/rv.h
View File

@ -56,6 +56,16 @@ DECLARE_EVENT_CLASS(error_da_monitor,
__entry->event,
__entry->state)
);
#ifdef CONFIG_RV_MON_WIP
DEFINE_EVENT(event_da_monitor, event_wip,
TP_PROTO(char *state, char *event, char *next_state, bool final_state),
TP_ARGS(state, event, next_state, final_state));
DEFINE_EVENT(error_da_monitor, error_wip,
TP_PROTO(char *state, char *event),
TP_ARGS(state, event));
#endif /* CONFIG_RV_MON_WIP */
#endif /* CONFIG_DA_MON_EVENTS_IMPLICIT */
#ifdef CONFIG_DA_MON_EVENTS_ID

13
kernel/trace/rv/Kconfig
View File

@ -25,6 +25,19 @@ menuconfig RV
For further information, see:
Documentation/trace/rv/runtime-verification.rst
config RV_MON_WIP
depends on RV
depends on PREEMPT_TRACER
select DA_MON_EVENTS_IMPLICIT
bool "wip monitor"
help
Enable wip (wakeup in preemptive) sample monitor that illustrates
the usage of per-cpu monitors, and one limitation of the
preempt_disable/enable events.
For further information, see:
Documentation/trace/rv/monitor_wip.rst
config RV_REACTORS
bool "Runtime verification reactors"
default y

1
kernel/trace/rv/Makefile
View File

@ -2,3 +2,4 @@
obj-$(CONFIG_RV) += rv.o
obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
obj-$(CONFIG_RV_MON_WIP) += monitors/wip/wip.o

51
kernel/trace/rv/monitors/wip/wip.c
View File

@ -10,44 +10,26 @@
#define MODULE_NAME "wip"
/*
* XXX: include required tracepoint headers, e.g.,
* #include <linux/trace/events/sched.h>
*/
#include <trace/events/rv.h>
#include <trace/events/sched.h>
#include <trace/events/preemptirq.h>
/*
* This is the self-generated part of the monitor. Generally, there is no need
* to touch this section.
*/
#include "wip.h"
/*
* Declare the deterministic automata monitor.
*
* The rv monitor reference is needed for the monitor declaration.
*/
struct rv_monitor rv_wip;
DECLARE_DA_MON_PER_CPU(wip, unsigned char);
/*
* This is the instrumentation part of the monitor.
*
* This is the section where manual work is required. Here the kernel events
* are translated into model's event.
*
*/
static void handle_preempt_disable(void *data, /* XXX: fill header */)
static void handle_preempt_disable(void *data, unsigned long ip, unsigned long parent_ip)
{
da_handle_event_wip(preempt_disable_wip);
}
static void handle_preempt_enable(void *data, /* XXX: fill header */)
static void handle_preempt_enable(void *data, unsigned long ip, unsigned long parent_ip)
{
da_handle_event_wip(preempt_enable_wip);
da_handle_start_event_wip(preempt_enable_wip);
}
static void handle_sched_waking(void *data, /* XXX: fill header */)
static void handle_sched_waking(void *data, struct task_struct *task)
{
da_handle_event_wip(sched_waking_wip);
}
@ -60,9 +42,9 @@ static int enable_wip(void)
if (retval)
return retval;
rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_disable);
rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_enable);
rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_sched_waking);
rv_attach_trace_probe("wip", preempt_enable, handle_preempt_enable);
rv_attach_trace_probe("wip", sched_waking, handle_sched_waking);
rv_attach_trace_probe("wip", preempt_disable, handle_preempt_disable);
return 0;
}
@ -71,19 +53,16 @@ static void disable_wip(void)
{
rv_wip.enabled = 0;
rv_detach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_disable);
rv_detach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_enable);
rv_detach_trace_probe("wip", /* XXX: tracepoint */, handle_sched_waking);
rv_detach_trace_probe("wip", preempt_disable, handle_preempt_disable);
rv_detach_trace_probe("wip", preempt_enable, handle_preempt_enable);
rv_detach_trace_probe("wip", sched_waking, handle_sched_waking);
da_monitor_destroy_wip();
}
/*
* This is the monitor register section.
*/
struct rv_monitor rv_wip = {
.name = "wip",
.description = "auto-generated wip",
.description = "wakeup in preemptive per-cpu testing monitor.",
.enable = enable_wip,
.disable = disable_wip,
.reset = da_monitor_reset_all_wip,
@ -105,5 +84,5 @@ module_init(register_wip);
module_exit(unregister_wip);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("dot2k: auto-generated");
MODULE_DESCRIPTION("wip");
MODULE_AUTHOR("Daniel Bristot de Oliveira <bristot@kernel.org>");
MODULE_DESCRIPTION("wip: wakeup in preemptive - per-cpu sample monitor.");

16
tools/verification/models/wip.dot Normal file
View File

@ -0,0 +1,16 @@
digraph state_automaton {
{node [shape = circle] "non_preemptive"};
{node [shape = plaintext, style=invis, label=""] "__init_preemptive"};
{node [shape = doublecircle] "preemptive"};
{node [shape = circle] "preemptive"};
"__init_preemptive" -> "preemptive";
"non_preemptive" [label = "non_preemptive"];
"non_preemptive" -> "non_preemptive" [ label = "sched_waking" ];
"non_preemptive" -> "preemptive" [ label = "preempt_enable" ];
"preemptive" [label = "preemptive"];
"preemptive" -> "non_preemptive" [ label = "preempt_disable" ];
{ rank = min ;
"__init_preemptive";
"preemptive";
}
}