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Really give priority to main_pid

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Do process all events as soon one for priority_pid arrives.

PiperOrigin-RevId: 553156575
Change-Id: I57a9b4ca54a0e0fe5f01245b130f53ef3f8678fc
This commit is contained in:
Wiktor Garbacz 2023-08-02 08:41:59 -07:00 committed by Copybara-Service
parent 3bbb98c494
commit 8fbe21ce0e
1 changed files with 29 additions and 19 deletions
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48
sandboxed_api/sandbox2/monitor_ptrace.cc
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@ -81,9 +81,7 @@ class PidWaiter {
// require attention at the moment, or -1 if there was an error, in which case
// the error value can be found in 'errno'.
int Wait(int* status) {
if (statuses_.empty() && last_errno_ == 0) {
RefillStatuses();
}
RefillStatuses();
if (statuses_.empty()) {
if (last_errno_ == 0) return 0;
@ -100,25 +98,37 @@ class PidWaiter {
}
private:
void RefillStatuses() {
statuses_.clear();
last_errno_ = 0;
pid_t pid = priority_pid_;
bool CheckStatus(pid_t pid) {
int status;
while (true) {
// It should be a non-blocking operation (hence WNOHANG), so this function
// returns quickly if there are no events to be processed.
pid_t ret =
waitpid(pid, &status, __WNOTHREAD | __WALL | WUNTRACED | WNOHANG);
if (ret > 0) {
statuses_.emplace_back(ret, status);
} else if (ret < 0) {
last_errno_ = errno;
break;
} else if (pid == -1) {
// It should be a non-blocking operation (hence WNOHANG), so this function
// returns quickly if there are no events to be processed.
pid_t ret =
waitpid(pid, &status, __WNOTHREAD | __WALL | WUNTRACED | WNOHANG);
if (ret < 0) {
last_errno_ = errno;
return true;
}
if (ret == 0) {
return false;
}
statuses_.emplace_back(ret, status);
return true;
}
void RefillStatuses() {
constexpr int kMaxIterations = 1000;
constexpr int kPriorityCheckPeriod = 100;
if (!statuses_.empty()) {
return;
}
for (int i = 0; last_errno_ == 0 && i < kMaxIterations; ++i) {
bool should_check_priority = (i % kPriorityCheckPeriod) == 0;
if (should_check_priority && CheckStatus(priority_pid_)) {
return;
}
if (!CheckStatus(-1)) {
break;
}
pid = -1;
}
}