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// Copyright 2019 The TCMalloc Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "tcmalloc/internal/util.h"
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <signal.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <utility>
#include "absl/time/clock.h"
#include "absl/time/time.h"
#include "tcmalloc/internal/logging.h"
GOOGLE_MALLOC_SECTION_BEGIN
namespace tcmalloc {
namespace tcmalloc_internal {
int signal_safe_open(const char* path, int flags, ...) {
int fd;
va_list ap;
va_start(ap, flags);
mode_t mode = va_arg(ap, mode_t);
va_end(ap);
do {
fd = ((flags & O_CREAT) ? open(path, flags, mode) : open(path, flags));
} while (fd == -1 && errno == EINTR);
return fd;
}
int signal_safe_close(int fd) {
int rc;
do {
rc = close(fd);
} while (rc == -1 && errno == EINTR);
return rc;
}
ssize_t signal_safe_write(int fd, const char* buf, size_t count,
size_t* bytes_written) {
ssize_t rc;
size_t total_bytes = 0;
do {
rc = write(fd, buf + total_bytes, count - total_bytes);
if (rc > 0) total_bytes += rc;
} while ((rc > 0 && count > total_bytes) || (rc == -1 && errno == EINTR));
if (bytes_written != nullptr) *bytes_written = total_bytes;
return rc;
}
int signal_safe_poll(struct pollfd* fds, int nfds, absl::Duration timeout) {
int rc = 0;
absl::Duration elapsed = absl::ZeroDuration();
// We can't use gettimeofday since it's not async signal safe. We could use
// clock_gettime but that would require linking //base against librt.
// Fortunately, timeout is of sufficiently coarse granularity that we can just
// approximate it.
while ((elapsed <= timeout || timeout < absl::ZeroDuration()) && (rc == 0)) {
if (elapsed > absl::ZeroDuration())
::absl::SleepFor(::absl::Milliseconds(1));
elapsed += absl::Milliseconds(1);
while ((rc = poll(fds, nfds, 0)) == -1 && errno == EINTR) {
}
}
return rc;
}
ssize_t signal_safe_read(int fd, char* buf, size_t count, size_t* bytes_read) {
ssize_t rc;
size_t total_bytes = 0;
struct pollfd pfd;
// poll is required for testing whether there is any data left on fd in the
// case of a signal interrupting a partial read. This is needed since this
// case is only defined to return the number of bytes read up to that point,
// with no indication whether more could have been read (up to count).
pfd.fd = fd;
pfd.events = POLL_IN;
pfd.revents = 0;
do {
rc = read(fd, buf + total_bytes, count - total_bytes);
if (rc > 0) total_bytes += rc;
if (rc == 0) break; // EOF
// try again if there's space to fill, no (non-interrupt) error,
// and data is available.
} while (total_bytes < count && (rc > 0 || errno == EINTR) &&
(signal_safe_poll(&pfd, 1, absl::ZeroDuration()) == 1 ||
total_bytes == 0));
if (bytes_read) *bytes_read = total_bytes;
if (rc != -1 || errno == EINTR)
rc = total_bytes; // return the cumulative bytes read
return rc;
}
std::vector<int> AllowedCpus() {
// We have no need for dynamically sized sets (currently >1024 CPUs for glibc)
// at the present time. We could change this in the future.
cpu_set_t allowed_cpus;
CHECK_CONDITION(sched_getaffinity(0, sizeof(allowed_cpus), &allowed_cpus) ==
0);
int n = CPU_COUNT(&allowed_cpus), c = 0;
std::vector<int> result(n);
for (int i = 0; i < CPU_SETSIZE && n; i++) {
if (CPU_ISSET(i, &allowed_cpus)) {
result[c++] = i;
n--;
}
}
CHECK_CONDITION(0 == n);
return result;
}
static cpu_set_t SpanToCpuSetT(absl::Span<int> mask) {
cpu_set_t result;
CPU_ZERO(&result);
for (int cpu : mask) {
CPU_SET(cpu, &result);
}
return result;
}
ScopedAffinityMask::ScopedAffinityMask(absl::Span<int> allowed_cpus) {
specified_cpus_ = SpanToCpuSetT(allowed_cpus);
// getaffinity should never fail.
CHECK_CONDITION(
sched_getaffinity(0, sizeof(original_cpus_), &original_cpus_) == 0);
// See destructor comments on setaffinity interactions. Tampered() will
// necessarily be true in this case.
sched_setaffinity(0, sizeof(specified_cpus_), &specified_cpus_);
}
ScopedAffinityMask::ScopedAffinityMask(int allowed_cpu) {
CPU_ZERO(&specified_cpus_);
CPU_SET(allowed_cpu, &specified_cpus_);
// getaffinity should never fail.
CHECK_CONDITION(
sched_getaffinity(0, sizeof(original_cpus_), &original_cpus_) == 0);
// See destructor comments on setaffinity interactions. Tampered() will
// necessarily be true in this case.
sched_setaffinity(0, sizeof(specified_cpus_), &specified_cpus_);
}
ScopedAffinityMask::~ScopedAffinityMask() {
// If something else has already reset our affinity, do not attempt to
// restrict towards our original mask. This is best-effort as the tampering
// may obviously occur during the destruction of *this.
if (!Tampered()) {
// Note: We do not assert success here, conflicts may restrict us from all
// 'original_cpus_'.
sched_setaffinity(0, sizeof(original_cpus_), &original_cpus_);
}
}
bool ScopedAffinityMask::Tampered() {
cpu_set_t current_cpus;
CHECK_CONDITION(sched_getaffinity(0, sizeof(current_cpus), ¤t_cpus) ==
0);
return !CPU_EQUAL(¤t_cpus, &specified_cpus_); // Mismatch => modified.
}
} // namespace tcmalloc_internal
} // namespace tcmalloc
GOOGLE_MALLOC_SECTION_END
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