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Message-ID: <20250721082325.71554-1-gmonaco@redhat.com>
Date: Mon, 21 Jul 2025 10:23:10 +0200
From: Gabriele Monaco <gmonaco@...hat.com>
To: linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Nam Cao <namcao@...utronix.de>
Cc: Gabriele Monaco <gmonaco@...hat.com>,
Tomas Glozar <tglozar@...hat.com>,
Juri Lelli <jlelli@...hat.com>,
Clark Williams <williams@...hat.com>,
John Kacur <jkacur@...hat.com>
Subject: [PATCH v4 00/14] rv: Add monitors to validate task switch
This series adds three monitors to the sched collection, extends and
replaces previously existing monitors:
{tss,snroc} => sts:
Not only prove that switches occur in scheduling context and scheduling
needs interrupt disabled but also that each call to the scheduler
disables interrupts to (optionally) switch.
nrp (NEW):
* preemption requires need resched which is cleared by any switch
(includes a non optimal workaround for /nested/ preemptions)
sssw (NEW):
* suspension requires setting the task to sleepable and, after the
switch occurs, the task requires a wakeup to come back to runnable
opid (NEW):
* waking and need-resched operations occur with interrupts and
preemption disabled or in IRQ without explicitly disabling preemption
Also include some minor cleanup patches (1-9) tracepoints (11) and
preparatory fixes (10) covering some corner cases:
The series is currently based on the next tree.
Patch 1 fixes the behaviour of the rv tool with -s and idle tasks.
Patch 2 allows the rv tool to gracefully terminate with SIGTERM
Patch 3 adds da_handle_start_run_event_ also to per-task monitors
Patch 4 removes a trailing whitespace from the rv tracepoint string
Patch 5 returns the registration error in all DA monitor instead of 0
Patch 6 fixes an out-of-bound memory access in DA tracepoints
Patch 7 adjusts monitors to have minimised Kconfig dependencies
Patch 8 properly orders nested monitors in the RV Kconfig file
Patch 9 adjusts dot2c not to create lines over 100 columns
Patch 10 detects race conditions when rv monitors run concurrently and
retries applying the events
Patch 11 adds the need_resched and removes unused arguments from
schedule entry/exit tracepoints
Patch 12 adds the sts monitor to replace tss and sncid
Patch 13 adds the nrp and sssw monitors
Patch 14 adds the opid monitor
NOTES
The nrp and sssw monitors include workarounds for racy conditions:
* A sleeping task requires to set the state to sleepable, but in case of
a task sleeping on an rtlock, the set sleepable and wakeup events race
and we don't always see the right order:
5d..2. 107.488369: event: 639: sleepable x set_sleepable -> sleepable
4d..5. 107.488369: event: 639: sleepable x wakeup -> running (final)
5d..3. 107.488385: error: 639: switch_suspend not expected in the state running
wakeup() set_state()
state=RUNNING
trace_set_state()
trace_wakeup()
state=SLEEPING
I added a special event (switch_block) but there may be a better way.
Taking a pi_lock in rtlock_slowlock_locked when setting the state to
TASK_RTLOCK_WAIT avoids this race, although this is likely not
something we want to do.
* I consider preemption any scheduling with preempt==true and assume
this can happen only if need resched is set.
In practice, however, we may see a preemption where the flag
is not set. This can happen in one specific condition:
need_resched
preempt_schedule()
preempt_schedule_irq()
__schedule()
!need_resched
__schedule()
We start a standard preemption (e.g. from preempt_enable when the flag
is set), an interrupts occurs before we schedule and, on its exit path,
it schedules, which clears the need_resched flag.
When the preempted task runs again, we continue the standard
preemption started earlier, although the flag is no longer set.
I added a workaround to allow the model not to fail in this condition,
by allowing a preemption without need_resched if an interrupt is
received. This might catch false negatives too.
Changes since V3 [1]:
* Fix condition for lines shorter than 100 columns in dot2c.
* Fix Kconfig tooltip for container monitors in rvgen.
* Improve condition not to skip pid-0 in userspace tool.
* Rearrange monitors to reduce needed tracepoints and arguments.
* Separately track errors when DAs run out of retries due to races.
* Fix issue in opid with multiple handlers in the same interrupt.
* Cleanup patches by removing, squashing and reordering.
Changes since RFC2:
* Arrange commits to prevent failed build while bisecting.
* Avoid dot2k generated files to reach the column limit. (Nam Cao)
* Rearrange and simplify da_monitor retry on racing events.
* Improve nrp monitor to handle /nested/ preemption on IRQ.
* Added minor patches (6-10).
* Cleanup and rearrange order.
Changes since RFC [2]:
* Remove wakeup tracepoint in try_to_block_task and use a different
flavour of sched_set_state
* Split the large srs monitor in two separate monitors for preemption
and sleep. These no longer have a concept of running task, they just
enforce the requirements for the different types of sched out.
* Restore the snroc monitor to describe the relationship between
generic sched out and sched in.
* Add opid monitor.
* Fix some build errors and cleanup.
[1] - https://lore.kernel.org/lkml/20250715071434.22508-1-gmonaco@redhat.com
[2] - https://lore.kernel.org/lkml/20250404084512.98552-11-gmonaco@redhat.com
To: Ingo Molnar <mingo@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>
To: Steven Rostedt <rostedt@...dmis.org>
To: Nam Cao <namcao@...utronix.de>
Cc: Tomas Glozar <tglozar@...hat.com>
Cc: Juri Lelli <jlelli@...hat.com>
Cc: Clark Williams <williams@...hat.com>
Cc: John Kacur <jkacur@...hat.com>
Gabriele Monaco (14):
tools/rv: Do not skip idle in trace
tools/rv: Stop gracefully also on SIGTERM
rv: Add da_handle_start_run_event_ to per-task monitors
rv: Remove trailing whitespace from tracepoint string
rv: Return init error when registering monitors
rv: Use strings in da monitors tracepoints
rv: Adjust monitor dependencies
verification/rvgen: Organise Kconfig entries for nested monitors
tools/dot2c: Fix generated files going over 100 column limit
rv: Retry when da monitor detects race conditions
sched: Adapt sched tracepoints for RV task model
rv: Replace tss and sncid monitors with more complete sts
rv: Add nrp and sssw per-task monitors
rv: Add opid per-cpu monitor
Documentation/trace/rv/monitor_sched.rst | 307 +++++++++++++++---
include/linux/rv.h | 3 +-
include/linux/sched.h | 7 +-
include/rv/da_monitor.h | 129 +++++---
include/trace/events/sched.h | 12 +-
kernel/sched/core.c | 13 +-
kernel/trace/rv/Kconfig | 16 +-
kernel/trace/rv/Makefile | 6 +-
kernel/trace/rv/monitors/{tss => nrp}/Kconfig | 12 +-
kernel/trace/rv/monitors/nrp/nrp.c | 138 ++++++++
kernel/trace/rv/monitors/nrp/nrp.h | 75 +++++
kernel/trace/rv/monitors/nrp/nrp_trace.h | 15 +
kernel/trace/rv/monitors/opid/Kconfig | 19 ++
kernel/trace/rv/monitors/opid/opid.c | 169 ++++++++++
kernel/trace/rv/monitors/opid/opid.h | 104 ++++++
.../sncid_trace.h => opid/opid_trace.h} | 8 +-
kernel/trace/rv/monitors/sched/Kconfig | 1 +
kernel/trace/rv/monitors/sched/sched.c | 3 +-
kernel/trace/rv/monitors/sco/sco.c | 7 +-
kernel/trace/rv/monitors/scpd/Kconfig | 2 +-
kernel/trace/rv/monitors/scpd/scpd.c | 7 +-
kernel/trace/rv/monitors/sncid/sncid.c | 96 ------
kernel/trace/rv/monitors/sncid/sncid.h | 49 ---
kernel/trace/rv/monitors/snep/Kconfig | 2 +-
kernel/trace/rv/monitors/snep/snep.c | 7 +-
kernel/trace/rv/monitors/snep/snep.h | 14 +-
kernel/trace/rv/monitors/snroc/snroc.c | 3 +-
.../trace/rv/monitors/{sncid => sssw}/Kconfig | 10 +-
kernel/trace/rv/monitors/sssw/sssw.c | 116 +++++++
kernel/trace/rv/monitors/sssw/sssw.h | 105 ++++++
kernel/trace/rv/monitors/sssw/sssw_trace.h | 15 +
kernel/trace/rv/monitors/sts/Kconfig | 19 ++
kernel/trace/rv/monitors/sts/sts.c | 156 +++++++++
kernel/trace/rv/monitors/sts/sts.h | 117 +++++++
.../{tss/tss_trace.h => sts/sts_trace.h} | 8 +-
kernel/trace/rv/monitors/tss/tss.c | 91 ------
kernel/trace/rv/monitors/tss/tss.h | 47 ---
kernel/trace/rv/monitors/wip/Kconfig | 2 +-
kernel/trace/rv/monitors/wip/wip.c | 3 +-
kernel/trace/rv/monitors/wwnr/wwnr.c | 3 +-
kernel/trace/rv/rv_trace.h | 114 ++++---
tools/verification/models/sched/nrp.dot | 29 ++
tools/verification/models/sched/opid.dot | 35 ++
tools/verification/models/sched/sncid.dot | 18 -
tools/verification/models/sched/sssw.dot | 30 ++
tools/verification/models/sched/sts.dot | 38 +++
tools/verification/models/sched/tss.dot | 18 -
tools/verification/rv/src/in_kernel.c | 4 +-
tools/verification/rv/src/rv.c | 1 +
tools/verification/rvgen/rvgen/container.py | 10 +
tools/verification/rvgen/rvgen/dot2c.py | 20 +-
tools/verification/rvgen/rvgen/generator.py | 16 +-
52 files changed, 1723 insertions(+), 526 deletions(-)
rename kernel/trace/rv/monitors/{tss => nrp}/Kconfig (51%)
create mode 100644 kernel/trace/rv/monitors/nrp/nrp.c
create mode 100644 kernel/trace/rv/monitors/nrp/nrp.h
create mode 100644 kernel/trace/rv/monitors/nrp/nrp_trace.h
create mode 100644 kernel/trace/rv/monitors/opid/Kconfig
create mode 100644 kernel/trace/rv/monitors/opid/opid.c
create mode 100644 kernel/trace/rv/monitors/opid/opid.h
rename kernel/trace/rv/monitors/{sncid/sncid_trace.h => opid/opid_trace.h} (66%)
delete mode 100644 kernel/trace/rv/monitors/sncid/sncid.c
delete mode 100644 kernel/trace/rv/monitors/sncid/sncid.h
rename kernel/trace/rv/monitors/{sncid => sssw}/Kconfig (58%)
create mode 100644 kernel/trace/rv/monitors/sssw/sssw.c
create mode 100644 kernel/trace/rv/monitors/sssw/sssw.h
create mode 100644 kernel/trace/rv/monitors/sssw/sssw_trace.h
create mode 100644 kernel/trace/rv/monitors/sts/Kconfig
create mode 100644 kernel/trace/rv/monitors/sts/sts.c
create mode 100644 kernel/trace/rv/monitors/sts/sts.h
rename kernel/trace/rv/monitors/{tss/tss_trace.h => sts/sts_trace.h} (67%)
delete mode 100644 kernel/trace/rv/monitors/tss/tss.c
delete mode 100644 kernel/trace/rv/monitors/tss/tss.h
create mode 100644 tools/verification/models/sched/nrp.dot
create mode 100644 tools/verification/models/sched/opid.dot
delete mode 100644 tools/verification/models/sched/sncid.dot
create mode 100644 tools/verification/models/sched/sssw.dot
create mode 100644 tools/verification/models/sched/sts.dot
delete mode 100644 tools/verification/models/sched/tss.dot
base-commit: d086c886ceb9f59dea6c3a9dae7eb89e780a20c9
--
2.50.1
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