The perf subsystem today unifies various tracing and monitoring
features, from both software and hardware. One benefit of the perf
subsystem is automatically inheriting events to child tasks, which
enables process-wide events monitoring with low overheads. By default
perf events are non-intrusive, not affecting behaviour of the tasks
being monitored.
For certain use-cases, however, it makes sense to leverage the
generality of the perf events subsystem and optionally allow the tasks
being monitored to receive signals on events they are interested in.
This patch series adds the option to synchronously signal user space on
events.
To better support process-wide synchronous self-monitoring, without
events propagating to children that do not share the current process's
shared environment, two pre-requisite patches are added to optionally
restrict inheritance to CLONE_THREAD, and remove events on exec (without
affecting the parent).
Examples how to use these features can be found in the tests added at
the end of the series. In addition to the tests added, the series has
also been subjected to syzkaller fuzzing (focus on 'kernel/events/'
coverage).
Motivation and Example Uses
---------------------------
1. Our immediate motivation is low-overhead sampling-based race
detection for user space [1]. By using perf_event_open() at
process initialization, we can create hardware
breakpoint/watchpoint events that are propagated automatically
to all threads in a process. As far as we are aware, today no
existing kernel facility (such as ptrace) allows us to set up
process-wide watchpoints with minimal overheads (that are
comparable to mprotect() of whole pages).
2. Other low-overhead error detectors that rely on detecting
accesses to certain memory locations or code, process-wide and
also only in a specific set of subtasks or threads.
[1] https://llvm.org/devmtg/2020-09/slides/Morehouse-GWP-Tsan.pdf
Other ideas for use-cases we found interesting, but should only
illustrate the range of potential to further motivate the utility (we're
sure there are more):
3. Code hot patching without full stop-the-world. Specifically, by
setting a code breakpoint to entry to the patched routine, then
send signals to threads and check that they are not in the
routine, but without stopping them further. If any of the
threads will enter the routine, it will receive SIGTRAP and
pause.
4. Safepoints without mprotect(). Some Java implementations use
"load from a known memory location" as a safepoint. When threads
need to be stopped, the page containing the location is
mprotect()ed and threads get a signal. This could be replaced with
a watchpoint, which does not require a whole page nor DTLB
shootdowns.
5. Threads receiving signals on performance events to
throttle/unthrottle themselves.
6. Tracking data flow globally.
Changelog
---------
v4:
* Fix for parent and child racing to exit in sync_child_event().
* Fix race between irq_work running and task's sighand being released by
release_task().
* Generalize setting si_perf and si_addr independent of event type;
introduces perf_event_attr::sig_data, which can be set by user space
to be propagated to si_perf.
* Warning in perf_sigtrap() if ctx->task and current mismatch; we expect
this on architectures that do not properly implement
arch_irq_work_raise().
* Require events that want sigtrap to be associated with a task.
* Dropped "perf: Add breakpoint information to siginfo on SIGTRAP"
in favor of more generic solution (perf_event_attr::sig_data).
v3:
* Add patch "perf: Rework perf_event_exit_event()" to beginning of
series, courtesy of Peter Zijlstra.
* Rework "perf: Add support for event removal on exec" based on
the added "perf: Rework perf_event_exit_event()".
* Fix kselftests to work with more recent libc, due to the way it forces
using the kernel's own siginfo_t.
* Add basic perf-tool built-in test.
v2/RFC: https://lkml.kernel.org/r/20210310104139.679618-1-elver@google.com
* Patch "Support only inheriting events if cloned with CLONE_THREAD"
added to series.
* Patch "Add support for event removal on exec" added to series.
* Patch "Add kselftest for process-wide sigtrap handling" added to
series.
* Patch "Add kselftest for remove_on_exec" added to series.
* Implicitly restrict inheriting events if sigtrap, but the child was
cloned with CLONE_CLEAR_SIGHAND, because it is not generally safe if
the child cleared all signal handlers to continue sending SIGTRAP.
* Various minor fixes (see details in patches).
v1/RFC: https://lkml.kernel.org/r/20210223143426.2412737-1-elver@google.com
Pre-series: The discussion at [2] led to the changes in this series. The
approach taken in "Add support for SIGTRAP on perf events" to trigger
the signal was suggested by Peter Zijlstra in [3].
[2] https://lore.kernel.org/lkml/CACT4Y+YPrXGw+AtESxAgPyZ84TYkNZdP0xpocX2jwVAbZ…
[3] https://lore.kernel.org/lkml/YBv3rAT566k+6zjg@hirez.programming.kicks-ass.n…
Marco Elver (9):
perf: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES to children
perf: Support only inheriting events if cloned with CLONE_THREAD
perf: Add support for event removal on exec
signal: Introduce TRAP_PERF si_code and si_perf to siginfo
perf: Add support for SIGTRAP on perf events
selftests/perf_events: Add kselftest for process-wide sigtrap handling
selftests/perf_events: Add kselftest for remove_on_exec
tools headers uapi: Sync tools/include/uapi/linux/perf_event.h
perf test: Add basic stress test for sigtrap handling
Peter Zijlstra (1):
perf: Rework perf_event_exit_event()
arch/m68k/kernel/signal.c | 3 +
arch/x86/kernel/signal_compat.c | 5 +-
fs/signalfd.c | 4 +
include/linux/compat.h | 2 +
include/linux/perf_event.h | 9 +-
include/linux/signal.h | 1 +
include/uapi/asm-generic/siginfo.h | 6 +-
include/uapi/linux/perf_event.h | 12 +-
include/uapi/linux/signalfd.h | 4 +-
kernel/events/core.c | 302 +++++++++++++-----
kernel/fork.c | 2 +-
kernel/signal.c | 11 +
tools/include/uapi/linux/perf_event.h | 12 +-
tools/perf/tests/Build | 1 +
tools/perf/tests/builtin-test.c | 5 +
tools/perf/tests/sigtrap.c | 150 +++++++++
tools/perf/tests/tests.h | 1 +
.../testing/selftests/perf_events/.gitignore | 3 +
tools/testing/selftests/perf_events/Makefile | 6 +
tools/testing/selftests/perf_events/config | 1 +
.../selftests/perf_events/remove_on_exec.c | 260 +++++++++++++++
tools/testing/selftests/perf_events/settings | 1 +
.../selftests/perf_events/sigtrap_threads.c | 210 ++++++++++++
23 files changed, 924 insertions(+), 87 deletions(-)
create mode 100644 tools/perf/tests/sigtrap.c
create mode 100644 tools/testing/selftests/perf_events/.gitignore
create mode 100644 tools/testing/selftests/perf_events/Makefile
create mode 100644 tools/testing/selftests/perf_events/config
create mode 100644 tools/testing/selftests/perf_events/remove_on_exec.c
create mode 100644 tools/testing/selftests/perf_events/settings
create mode 100644 tools/testing/selftests/perf_events/sigtrap_threads.c
--
2.31.0.208.g409f899ff0-goog
From: SeongJae Park <sjpark(a)amazon.de>
When running a test program, 'run_one()' checks if the program has the
execution permission and fails if it doesn't. However, it's easy to
mistakenly missing the permission, as some common tools like 'diff'
don't support the permission change well[1]. Compared to that, making
mistakes in the test program's path would only rare, as those are
explicitly listed in 'TEST_PROGS'. Therefore, it might make more sense
to resolve the situation on our own and run the program.
For the reason, this commit makes the test program runner function to
still print the warning message but try parsing the interpreter of the
program and explicitly run it with the interpreter, in the case.
[1] https://lore.kernel.org/mm-commits/YRJisBs9AunccCD4@kroah.com/
Suggested-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>
Signed-off-by: SeongJae Park <sjpark(a)amazon.de>
---
Changes from v1
(https://lore.kernel.org/linux-kselftest/20210810140459.23990-1-sj38.park@gm…)
- Parse and use the interpreter instead of changing the file
tools/testing/selftests/kselftest/runner.sh | 28 +++++++++++++--------
1 file changed, 18 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/kselftest/runner.sh b/tools/testing/selftests/kselftest/runner.sh
index cc9c846585f0..a9ba782d8ca0 100644
--- a/tools/testing/selftests/kselftest/runner.sh
+++ b/tools/testing/selftests/kselftest/runner.sh
@@ -33,9 +33,9 @@ tap_timeout()
{
# Make sure tests will time out if utility is available.
if [ -x /usr/bin/timeout ] ; then
- /usr/bin/timeout --foreground "$kselftest_timeout" "$1"
+ /usr/bin/timeout --foreground "$kselftest_timeout" $1
else
- "$1"
+ $1
fi
}
@@ -65,17 +65,25 @@ run_one()
TEST_HDR_MSG="selftests: $DIR: $BASENAME_TEST"
echo "# $TEST_HDR_MSG"
- if [ ! -x "$TEST" ]; then
- echo -n "# Warning: file $TEST is "
- if [ ! -e "$TEST" ]; then
- echo "missing!"
- else
- echo "not executable, correct this."
- fi
+ if [ ! -e "$TEST" ]; then
+ echo "# Warning: file $TEST is missing!"
echo "not ok $test_num $TEST_HDR_MSG"
else
+ cmd="./$BASENAME_TEST"
+ if [ ! -x "$TEST" ]; then
+ echo "# Warning: file $TEST is not executable"
+
+ if [ $(head -n 1 "$TEST" | cut -c -2) = "#!" ]
+ then
+ interpreter=$(head -n 1 "$TEST" | cut -c 3-)
+ cmd="$interpreter ./$BASENAME_TEST"
+ else
+ echo "not ok $test_num $TEST_HDR_MSG"
+ return
+ fi
+ fi
cd `dirname $TEST` > /dev/null
- ((((( tap_timeout ./$BASENAME_TEST 2>&1; echo $? >&3) |
+ ((((( tap_timeout "$cmd" 2>&1; echo $? >&3) |
tap_prefix >&4) 3>&1) |
(read xs; exit $xs)) 4>>"$logfile" &&
echo "ok $test_num $TEST_HDR_MSG") ||
--
2.17.1
Real-time setups try hard to ensure proper isolation between time
critical applications and e.g. network processing performed by the
network stack in softirq and RPS is used to move the softirq
activity away from the isolated core.
If the network configuration is dynamic, with netns and devices
routinely created at run-time, enforcing the correct RPS setting
on each newly created device allowing to transient bad configuration
became complex.
These series try to address the above, introducing a new
sysctl knob: rps_default_mask. The new sysctl entry allows
configuring a systemwide RPS mask, to be enforced since receive
queue creation time without any fourther per device configuration
required.
Additionally, a simple self-test is introduced to check the
rps_default_mask behavior.
v1 -> v2:
- fix sparse warning in patch 2/3
Paolo Abeni (3):
net/sysctl: factor-out netdev_rx_queue_set_rps_mask() helper
net/core: introduce default_rps_mask netns attribute
self-tests: introduce self-tests for RPS default mask
Documentation/admin-guide/sysctl/net.rst | 6 ++
include/linux/netdevice.h | 1 +
net/core/net-sysfs.c | 73 +++++++++++--------
net/core/sysctl_net_core.c | 58 +++++++++++++++
tools/testing/selftests/net/Makefile | 1 +
tools/testing/selftests/net/config | 3 +
.../testing/selftests/net/rps_default_mask.sh | 57 +++++++++++++++
7 files changed, 169 insertions(+), 30 deletions(-)
create mode 100755 tools/testing/selftests/net/rps_default_mask.sh
--
2.26.2
From: Vincent Cheng <vincent.cheng.xh(a)renesas.com>
This series adds adjust phase to the PTP Hardware Clock device interface.
Some PTP hardware clocks have a write phase mode that has
a built-in hardware filtering capability. The write phase mode
utilizes a phase offset control word instead of a frequency offset
control word. Add adjust phase function to take advantage of this
capability.
Changes since v1:
- As suggested by Richard Cochran:
1. ops->adjphase is new so need to check for non-null function pointer.
2. Kernel coding style uses lower_case_underscores.
3. Use existing PTP clock API for delayed worker.
Vincent Cheng (3):
ptp: Add adjphase function to support phase offset control.
ptp: Add adjust_phase to ptp_clock_caps capability.
ptp: ptp_clockmatrix: Add adjphase() to support PHC write phase mode.
drivers/ptp/ptp_chardev.c | 1 +
drivers/ptp/ptp_clock.c | 3 ++
drivers/ptp/ptp_clockmatrix.c | 92 +++++++++++++++++++++++++++++++++++
drivers/ptp/ptp_clockmatrix.h | 8 ++-
include/linux/ptp_clock_kernel.h | 6 ++-
include/uapi/linux/ptp_clock.h | 4 +-
tools/testing/selftests/ptp/testptp.c | 6 ++-
7 files changed, 114 insertions(+), 6 deletions(-)
--
2.7.4
Hello Juergen,
Hello All,
Since the RC1 of kernel 5.13, -smp 2 and -smp 4 don't work with a
virtual e5500 QEMU KVM-HV machine anymore. [1]
I see in the serial console, that the uImage doesn't load. I use the
following QEMU command for booting:
qemu-system-ppc64 -M ppce500 -cpu e5500 -enable-kvm -m 1024 -kernel
uImage -drive format=raw,file=MintPPC32-X5000.img,index=0,if=virtio
-netdev user,id=mynet0 -device virtio-net,netdev=mynet0 -append "rw
root=/dev/vda" -device virtio-vga -device virtio-mouse-pci -device
virtio-keyboard-pci -device pci-ohci,id=newusb -device
usb-audio,bus=newusb.0 -smp 4
The kernels boot without KVM-HV.
Summary for KVM-HV:
-smp 1 -> works
-smp 2 -> doesn't work
-smp 3 -> works
-smp 4 -> doesn't work
I used -smp 4 before the RC1 of kernel 5.13 because my FSL P5040 BookE
machine [2] has 4 cores.
Does this patch solve this issue? [3]
Thanks,
Christian
[1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2021-May/229103.html
[2] http://wiki.amiga.org/index.php?title=X5000
[3]
https://lists.ozlabs.org/pipermail/linuxppc-dev/2021-September/234152.html
On this v9 I've dropped the generic sysfs deadlock fix given Ming Lei
has provided alternative fixes for the zram driver without incurring
a generic lock *and* we don't yet have full assessment of how wide
spread the deadlock case might be in the kernel. A full assessment
effort is still underway using Coccinelle with iteration support,
however that effort will take a bit more time to complete. We can
re-evaluate the value of a generic fix later after the assessment
is complete.
This series now just adds the test_sysfs selftest and failure injection
support for it on kernfs. The most valuable tests are those which
confirm that once a kernfs active reference is obtained with
kernfs_get_active() the pointers used there are still valid, and so
using sysfs ops *are* safe if we race against module removal. Likewise
it also confirms how module removal will *wait* for these ops to
complete if a kernfs node is already active.
This v9 series also addresses feedback mostly provided by Kees Cook and Greg.
I also made a few changes to the test_sysfs driver to account for changes in
the block layer. I also improved the kernfs failure injection tests with
documentation of how they work and to account for the real expected return
value of a write before the kernfs active reference is obtained. Upstream
commit 8e141f9eb803e ("block: drain file system I/O on del_gendisk") has
revealed that small minor induced delays on del_gendisk() can make a few
writes succeed if the delays used are small. So we clarify the logic of why
writes could either fail or succeed before the kernfs active reference is taken.
These changes also availble on this tree:
https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/log/?…
v9:
* rebased onto linux-next tag next-20211029
* add Reviewed-by tags for the SPDX change, and the drivers which
get the tag for it
* drop the generic sysfs deadlock fix for now as the scope of how
wide spread the issue is still needs to be assessed
* drop the zram patches as they are replaced by Ming Lei's fixes
* drop already merged patches
* try_module_get() docs: enhanced using feedback from Kees Cook. I
extended the documention to make it clear that if proper care is not
taken the use of this routine could crash the kernel.
* kernfs: move failure injection knobs under /sys/kernel/debug/fail_kernfs
as suggested by Kees Cook
* kernfs: rename failure injection file to fault_inject.c as suggested
by Kees Cook
* kernfs: split up documentation of failure injection knobs as
suggested by Kees Cook
* kernfs: move the wait into debug call, and use a simple one liner
may_wait() calls to make the changes much less intrusive and more
readable as suggested by Kees Cook
* kernfs: drop __func__ uses as suggested by Kees Cook
* test_sysfs: use sizeof() instead of open coded 16 as suggested by
Kees Cook
* test_sysfs: use sysfs_emit as suggested by Kees Cook
* test_sysfs: drop boiler place license as suggested by Greg KH
* test_sysfs: use depends instead of select as suggested by Kees Cook
* test_sysfs: drop #ifdefery as suggested by Kees Cook
* test_sysfs: clarified that the use of a lock on rmmod which causes
a deadlock is something drivers should avoid, and its why we leave
the test disabled.
* test_sysfs: now that device_add_disk() returns an error, use the
new error return code, otherwise this is going to prevent us from
eventually embracing __must_check() on that call on the block layer.
* test_syfs: testdev_submit_bio() needed to change data types as now
it returns void.
* test_sysfs: enhance kernfs failure injection tests with documenation
and correct the expected return value for writes
Luis Chamberlain (6):
LICENSES: Add the copyleft-next-0.3.1 license
testing: use the copyleft-next-0.3.1 SPDX tag
selftests: add tests_sysfs module
kernfs: add initial failure injection support
test_sysfs: add support to use kernfs failure injection
kernel/module: add documentation for try_module_get()
.../fault-injection/fault-injection.rst | 50 +
LICENSES/dual/copyleft-next-0.3.1 | 237 +++
MAINTAINERS | 9 +-
fs/kernfs/Makefile | 1 +
fs/kernfs/fault_inject.c | 93 ++
fs/kernfs/file.c | 9 +
fs/kernfs/kernfs-internal.h | 70 +
include/linux/kernfs.h | 5 +
include/linux/module.h | 37 +-
lib/Kconfig.debug | 23 +
lib/Makefile | 1 +
lib/test_kmod.c | 12 +-
lib/test_sysctl.c | 12 +-
lib/test_sysfs.c | 913 +++++++++++
tools/testing/selftests/kmod/kmod.sh | 13 +-
tools/testing/selftests/sysctl/sysctl.sh | 12 +-
tools/testing/selftests/sysfs/Makefile | 12 +
tools/testing/selftests/sysfs/config | 5 +
tools/testing/selftests/sysfs/settings | 1 +
tools/testing/selftests/sysfs/sysfs.sh | 1411 +++++++++++++++++
20 files changed, 2878 insertions(+), 48 deletions(-)
create mode 100644 LICENSES/dual/copyleft-next-0.3.1
create mode 100644 fs/kernfs/fault_inject.c
create mode 100644 lib/test_sysfs.c
create mode 100644 tools/testing/selftests/sysfs/Makefile
create mode 100644 tools/testing/selftests/sysfs/config
create mode 100644 tools/testing/selftests/sysfs/settings
create mode 100755 tools/testing/selftests/sysfs/sysfs.sh
--
2.30.2