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Lisa Robinson
96702d68ec
When validating a perf event group, validate_group() unconditionally
attempts to allocate hardware PMU counters for the leader, sibling
events and the new event being added.
This is incorrect for mixed-type groups. If a PERF_TYPE_SOFTWARE event
is part of the group, the current code still tries to allocate a hardware
PMU counter for it, which can wrongly consume hardware PMU resources and
cause spurious allocation failures.
Fix this by only allocating PMU counters for hardware events during group
validation, and skipping software events.
A trimmed down reproducer is as simple as this:
#include <stdio.h>
#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <sys/syscall.h>
#include <linux/perf_event.h>
int main (int argc, char *argv[])
{
struct perf_event_attr attr = { 0 };
int fds[5];
attr.disabled = 1;
attr.exclude_kernel = 1;
attr.exclude_hv = 1;
attr.read_format = PERF_FORMAT_TOTAL_TIME_ENABLED |
PERF_FORMAT_TOTAL_TIME_RUNNING | PERF_FORMAT_ID | PERF_FORMAT_GROUP;
attr.size = sizeof (attr);
attr.type = PERF_TYPE_SOFTWARE;
attr.config = PERF_COUNT_SW_DUMMY;
fds[0] = syscall (SYS_perf_event_open, &attr, 0, -1, -1, 0);
assert (fds[0] >= 0);
attr.type = PERF_TYPE_HARDWARE;
attr.config = PERF_COUNT_HW_CPU_CYCLES;
fds[1] = syscall (SYS_perf_event_open, &attr, 0, -1, fds[0], 0);
assert (fds[1] >= 0);
attr.type = PERF_TYPE_HARDWARE;
attr.config = PERF_COUNT_HW_INSTRUCTIONS;
fds[2] = syscall (SYS_perf_event_open, &attr, 0, -1, fds[0], 0);
assert (fds[2] >= 0);
attr.type = PERF_TYPE_HARDWARE;
attr.config = PERF_COUNT_HW_BRANCH_MISSES;
fds[3] = syscall (SYS_perf_event_open, &attr, 0, -1, fds[0], 0);
assert (fds[3] >= 0);
attr.type = PERF_TYPE_HARDWARE;
attr.config = PERF_COUNT_HW_CACHE_REFERENCES;
fds[4] = syscall (SYS_perf_event_open, &attr, 0, -1, fds[0], 0);
assert (fds[4] >= 0);
printf ("PASSED\n");
return 0;
}
Cc: stable@vger.kernel.org
Fixes: b37042b2bb7c ("LoongArch: Add perf events support")
Signed-off-by: Lisa Robinson <lisa@bytefly.space>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.