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