Userspace: Deal with select() returning EINTR on a signal interruption

Add a trivial CSafeSyscall template that calls a callback until it stops
returning EINTR, and use it everywhere we use select() now.

Thanks to Andreas for the suggestion of using a template parameter for
the syscall function to invoke.

Libraries/LibCore/CEventLoop.cpp

@@ -4,6 +4,7 @@
 #include <LibCore/CLock.h>
 #include <LibCore/CNotifier.h>
 #include <LibCore/CObject.h>
+#include <LibCore/CSyscallUtils.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
@@ -203,11 +204,7 @@ void CEventLoop::wait_for_event(WaitMode mode)
         should_wait_forever = false;
     }
 
-    int marked_fd_count = select(max_fd + 1, &rfds, &wfds, nullptr, should_wait_forever ? nullptr : &timeout);
-    if (marked_fd_count < 0) {
-        ASSERT_NOT_REACHED();
-    }
-
+    int marked_fd_count = CSyscallUtils::safe_syscall(select, max_fd + 1, &rfds, &wfds, nullptr, should_wait_forever ? nullptr : &timeout);
     if (FD_ISSET(s_wake_pipe_fds[0], &rfds)) {
         char buffer[32];
         auto nread = read(s_wake_pipe_fds[0], buffer, sizeof(buffer));

Libraries/LibCore/CIODevice.cpp

@@ -1,5 +1,6 @@
 #include <AK/PrintfImplementation.h>
 #include <LibCore/CIODevice.h>
+#include <LibCore/CSyscallUtils.h>
 #include <errno.h>
 #include <stdio.h>
 #include <sys/select.h>
@@ -71,7 +72,7 @@ bool CIODevice::can_read_from_fd() const
     struct timeval timeout {
         0, 0
     };
-    int rc = select(m_fd + 1, &rfds, nullptr, nullptr, &timeout);
+    int rc = CSyscallUtils::safe_syscall(select, m_fd + 1, &rfds, nullptr, nullptr, &timeout);
     if (rc < 0) {
         // NOTE: We don't set m_error here.
         perror("CIODevice::can_read: select");

Libraries/LibCore/CSyscallUtils.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <AK/StdLibExtras.h>
+
+namespace CSyscallUtils {
+
+template <typename Syscall, class... Args>
+inline int safe_syscall(Syscall syscall, Args&& ... args) {
+    for (;;) {
+        int sysret = syscall(forward<Args>(args)...);
+        if (sysret == -1) {
+            dbgprintf("CSafeSyscall: %d (%d: %s)\n", sysret, errno, strerror(errno));
+            if (errno == EINTR)
+                continue;
+            ASSERT_NOT_REACHED();
+        }
+        return sysret;
+    }
+}
+
+}
+

Libraries/LibCore/CoreIPCClient.h

@@ -3,6 +3,7 @@
 #include <LibCore/CEventLoop.h>
 #include <LibCore/CEvent.h>
 #include <LibCore/CLocalSocket.h>
+#include <LibCore/CSyscallUtils.h>
 #include <LibCore/CNotifier.h>
 #include <LibAudio/ASAPI.h>
 
@@ -106,7 +107,7 @@ public:
             fd_set rfds;
             FD_ZERO(&rfds);
             FD_SET(m_connection.fd(), &rfds);
-            int rc = select(m_connection.fd() + 1, &rfds, nullptr, nullptr, nullptr);
+            int rc = CSyscallUtils::safe_syscall(select, m_connection.fd() + 1, &rfds, nullptr, nullptr, nullptr);
             if (rc < 0) {
                 perror("select");
             }

Servers/LookupServer/main.cpp

@@ -8,6 +8,7 @@
 #include <Kernel/Net/IPv4.h>
 #include <LibCore/CConfigFile.h>
 #include <LibCore/CFile.h>
+#include <LibCore/CSyscallUtils.h>
 #include <arpa/inet.h>
 #include <netinet/in.h>
 #include <stdio.h>
@@ -108,7 +109,7 @@ int main(int argc, char** argv)
         fd_set rfds;
         FD_ZERO(&rfds);
         FD_SET(server_fd, &rfds);
-        rc = select(server_fd + 1, &rfds, nullptr, nullptr, nullptr);
+        rc = CSyscallUtils::safe_syscall(select, server_fd + 1, &rfds, nullptr, nullptr, nullptr);
         if (rc < 1) {
             perror("select");
             return 1;