commit 43323a7e7a4ce39a89d55f0b27f4570d711bddce
author Bart Van Assche <bvanassche@google.com> Fri Nov 03 10:07:59 2023 -0700
committer Bart Van Assche <bvanassche@google.com> Mon Nov 06 10:38:20 2023 -0800
tree 8db2a705a8e68fbb8e6582cce81dd21b11832646
parent 6c7dca816fda695a4d6d719e29aa193d39510823

init: Create different file descriptors for SIGCHLD and SIGTERM

This change will allow a later CL to wait for SIGCHLD without discarding
the SIGTERM information.

Bug: 308687042
Change-Id: I5b9ab4562060455573cd816cc48bf90576b39ab9
Signed-off-by: Bart Van Assche <bvanassche@google.com>

init/init.cpp

diff --git a/init/init.cpp b/init/init.cpp
index 19f34da..68701aa 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -108,6 +108,7 @@
 using android::base::StringPrintf;
 using android::base::Timer;
 using android::base::Trim;
+using android::base::unique_fd;
 using android::fs_mgr::AvbHandle;
 using android::snapshot::SnapshotManager;
 
@@ -116,7 +117,8 @@
 
 static int property_triggers_enabled = 0;
 
-static int signal_fd = -1;
+static int sigchld_fd = -1;
+static int sigterm_fd = -1;
 static int property_fd = -1;
 
 struct PendingControlMessage {
@@ -713,8 +715,9 @@
     HandlePowerctlMessage("shutdown,container");
 }
 
-static void HandleSignalFd() {
+static void HandleSignalFd(int signal) {
     signalfd_siginfo siginfo;
+    const int signal_fd = signal == SIGCHLD ? sigchld_fd : sigterm_fd;
     ssize_t bytes_read = TEMP_FAILURE_RETRY(read(signal_fd, &siginfo, sizeof(siginfo)));
     if (bytes_read != sizeof(siginfo)) {
         PLOG(ERROR) << "Failed to read siginfo from signal_fd";
@@ -748,6 +751,24 @@
     }
 }
 
+static Result<int> CreateAndRegisterSignalFd(Epoll* epoll, int signal) {
+    sigset_t mask;
+    sigemptyset(&mask);
+    sigaddset(&mask, signal);
+    unique_fd signal_fd(signalfd(-1, &mask, SFD_CLOEXEC));
+    if (signal_fd == -1) {
+        return ErrnoError() << "failed to create signalfd for signal " << signal;
+    }
+
+    auto result = epoll->RegisterHandler(
+            signal_fd.get(), [signal]() { HandleSignalFd(signal); }, EPOLLIN | EPOLLPRI);
+    if (!result.ok()) {
+        return result.error();
+    }
+
+    return signal_fd.release();
+}
+
 static void InstallSignalFdHandler(Epoll* epoll) {
     // Applying SA_NOCLDSTOP to a defaulted SIGCHLD handler prevents the signalfd from receiving
     // SIGCHLD when a child process stops or continues (b/77867680#comment9).
@@ -774,14 +795,18 @@
         LOG(FATAL) << "Failed to register a fork handler: " << strerror(result);
     }
 
-    signal_fd = signalfd(-1, &mask, SFD_CLOEXEC);
-    if (signal_fd == -1) {
-        PLOG(FATAL) << "failed to create signalfd";
+    Result<int> cs_result = CreateAndRegisterSignalFd(epoll, SIGCHLD);
+    if (!cs_result.ok()) {
+        PLOG(FATAL) << cs_result.error();
     }
+    sigchld_fd = cs_result.value();
 
-    constexpr int flags = EPOLLIN | EPOLLPRI;
-    if (auto result = epoll->RegisterHandler(signal_fd, HandleSignalFd, flags); !result.ok()) {
-        LOG(FATAL) << result.error();
+    if (sigismember(&mask, SIGTERM)) {
+        Result<int> cs_result = CreateAndRegisterSignalFd(epoll, SIGTERM);
+        if (!cs_result.ok()) {
+            PLOG(FATAL) << cs_result.error();
+        }
+        sigterm_fd = cs_result.value();
     }
 }