global/signal_handler: use poll(2) instead of select(2)

Starting with commit 61a298c39c1a6684682e2b749e45a66d073182c8 we delay the
signal handler setup until after lots of other initialization has happened,
which can result in us having very large (>1024) open fds, which will
break the FD_SET macros for select(2).  Use poll(2) instead.

Fixes: #5722
Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>

diff --git a/src/global/signal_handler.cc b/src/global/signal_handler.cc
index 25f1a0a1992938f354456142fe63e143b52ff0bc..d403637002b15f78406397fcd1a457d8298e0dbe 100644 (file)
--- a/src/global/signal_handler.cc
+++ b/src/global/signal_handler.cc
@@ -19,6 +19,7 @@
 #include "global/pidfile.h"
 #include "global/signal_handler.h"
 
+#include <poll.h>
 #include <signal.h>
 #include <sstream>
 #include <stdlib.h>
@@ -189,25 +190,23 @@ struct SignalHandler : public Thread {
   // thread entry point
   void *entry() {
     while (!stop) {
-      // create fd set
-      fd_set rfds;
-      FD_ZERO(&rfds);
-      FD_SET(pipefd[0], &rfds);
-      int max_fd = pipefd[0];
+      // build fd list
+      struct pollfd fds[33];
 
       lock.Lock();
+      int num_fds = 0;
       for (unsigned i=0; i<32; i++) {
        if (handlers[i]) {
-         int fd = handlers[i]->pipefd[0];
-         FD_SET(fd, &rfds);
-         if (fd > max_fd)
-           max_fd = fd;
+         fds[num_fds].fd = handlers[i]->pipefd[0];
+         fds[num_fds].events = POLLIN | POLLOUT | POLLERR;
+         fds[num_fds].revents = 0;
+         ++num_fds;
        }
       }
       lock.Unlock();
 
       // wait for data on any of those pipes
-      int r = select(max_fd + 1, &rfds, NULL, NULL, NULL);
+      int r = poll(fds, num_fds, -1);
       if (stop)
        break;
       if (r > 0) {

diff --git a/src/test/signals.cc b/src/test/signals.cc
index 437549885599daafa6be4b133370ffeeb8263f11..2c7f4d32a0af85fcee62e270d3120d0f93452afe 100644 (file)
--- a/src/test/signals.cc
+++ b/src/test/signals.cc
@@ -110,3 +110,33 @@ TEST(SignalHandler, Multiple)
   unregister_async_signal_handler(SIGUSR2, testhandler);
   shutdown_async_signal_handler();
 }
+
+/*
+TEST(SignalHandler, MultipleBigFd)
+{
+  int ret;
+
+  for (int i = 0; i < 1500; i++)
+    ::open(".", O_RDONLY);
+
+  reset();
+  init_async_signal_handler();
+  register_async_signal_handler(SIGUSR1, testhandler);
+  register_async_signal_handler(SIGUSR2, testhandler);
+  ASSERT_TRUE(usr1 == false);
+  ASSERT_TRUE(usr2 == false);
+
+  ret = kill(getpid(), SIGUSR1);
+  ASSERT_EQ(ret, 0);
+  ret = kill(getpid(), SIGUSR2);
+  ASSERT_EQ(ret, 0);
+
+  sleep(1);
+  ASSERT_TRUE(usr1 == true);
+  ASSERT_TRUE(usr2 == true);
+
+  unregister_async_signal_handler(SIGUSR1, testhandler);
+  unregister_async_signal_handler(SIGUSR2, testhandler);
+  shutdown_async_signal_handler();
+}
+*/