commit 97047b54e952e2d08b10e6d37d510ca653cace00
author Bart Van Assche <bvanassche@google.com> Thu Nov 16 12:42:35 2023 -0800
committer Bart Van Assche <bvanassche@google.com> Mon Nov 20 09:32:59 2023 -0800
tree 0b3a5fc7989ad9905f5688830f57e22235c85ead
parent ced62e53eda45387d06c55c155c6bbef8a80a8a0

init: Combine two global sigchld_fd variables into one

Remove the Service::SetSigchldFd() method. Make the Service::GetSigchldFd()
create a signalfd for SIGCHLD. This makes it possible to use a SIGCHLD
signalfd in unit tests.

Change-Id: I0b41caa8f46c79f4d400e49aaba5227fad53c251
Signed-off-by: Bart Van Assche <bvanassche@google.com>

init/service.cpp

diff --git a/init/service.cpp b/init/service.cpp
index d351a8f..eb24dd5 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -37,6 +37,7 @@
 #include <cutils/sockets.h>
 #include <processgroup/processgroup.h>
 #include <selinux/selinux.h>
+#include <sys/signalfd.h>
 
 #include <string>
 
@@ -68,6 +69,7 @@
 using android::base::SetProperty;
 using android::base::StartsWith;
 using android::base::StringPrintf;
+using android::base::unique_fd;
 using android::base::WriteStringToFile;
 
 namespace android {
@@ -136,7 +138,6 @@
 
 unsigned long Service::next_start_order_ = 1;
 bool Service::is_exec_service_running_ = false;
-int Service::sigchld_fd_ = -1;
 
 Service::Service(const std::string& name, Subcontext* subcontext_for_restart_commands,
                  const std::string& filename, const std::vector<std::string>& args)
@@ -792,6 +793,35 @@
     mount_namespace_ = IsDefaultMountNamespaceReady() ? NS_DEFAULT : NS_BOOTSTRAP;
 }
 
+static int ThreadCount() {
+    std::unique_ptr<DIR, decltype(&closedir)> dir(opendir("/proc/self/task"), closedir);
+    if (!dir) {
+        return -1;
+    }
+
+    int count = 0;
+    dirent* entry;
+    while ((entry = readdir(dir.get())) != nullptr) {
+        if (entry->d_name[0] != '.') {
+            count++;
+        }
+    }
+    return count;
+}
+
+// Must be called BEFORE any threads are created. See also the sigprocmask() man page.
+unique_fd Service::CreateSigchldFd() {
+    CHECK_EQ(ThreadCount(), 1);
+    sigset_t mask;
+    sigemptyset(&mask);
+    sigaddset(&mask, SIGCHLD);
+    if (sigprocmask(SIG_BLOCK, &mask, nullptr) < 0) {
+        PLOG(FATAL) << "Failed to block SIGCHLD";
+    }
+
+    return unique_fd(signalfd(-1, &mask, SFD_CLOEXEC));
+}
+
 void Service::SetStartedInFirstStage(pid_t pid) {
     LOG(INFO) << "adding first-stage service '" << name_ << "'...";