Add FD exhaustion logging for Chrome OS.

base/memory/shared_memory_helper.cc

Index: base/memory/shared_memory_helper.cc
diff --git a/base/memory/shared_memory_helper.cc b/base/memory/shared_memory_helper.cc
index e80083cf78d4e26550c6c9ff99b48f12e8087d1b..75fa97cfef5fb9fcb270b1b06c24696faa27739c 100644
--- a/base/memory/shared_memory_helper.cc
+++ b/base/memory/shared_memory_helper.cc
@@ -4,6 +4,11 @@
 
 #include "base/memory/shared_memory_helper.h"
 
+#if defined(OS_CHROMEOS)
+#include <sys/resource.h>
+#include <sys/time.h>
+#endif  // defined(OS_CHROMEOS)
+
 #include "base/threading/thread_restrictions.h"
 
 namespace base {
@@ -90,6 +95,43 @@ bool PrepareMapFile(ScopedFILE fp,
   *mapped_file = HANDLE_EINTR(dup(fileno(fp.get())));
   if (*mapped_file == -1) {
     NOTREACHED() << "Call to dup failed, errno=" << errno;
+#if defined(OS_CHROMEOS)
+    if (errno == EMFILE) {
+      // We're out of file descriptors and are probably about to crash somewhere
+      // else in Chrome anyway. Let's collect what FD information we can and
+      // crash.
+      // Added for debugging crbug.com/733718
+      struct rlimit rlim;
+      if (getrlimit(RLIMIT_NOFILE, &rlim) == 0) {
+        if (rlim.rlim_max > rlim.rlim_cur) {
+          // Increase fd limit so breakpad has a chance to write a minidump.
+          rlim.rlim_cur = rlim.rlim_max;
+          if (setrlimit(RLIMIT_NOFILE, &rlim) != 0) {
+            PLOG(ERROR) << "setrlimit() failed";
+          }
+        }
+        PLOG(ERROR) << "getrlimit() failed";
+
+        // Fall back to 16K if we can't call getrlimit().
+        rlim.rlim_cur = 16384;

[Daniel Erat, 2017/06/29 19:26:04]

i think you meant for this (and the PLOG(ERROR) above) to be in an else block if
the getrlimit call fails, right?

[teravest, 2017/06/29 19:50:25]

Yep. Fixed, thanks.

+      }
+
+      char buf[PATH_MAX];
+      char fd_path[PATH_MAX];
+      for (int i = 0; i < static_cast<int>(rlim.rlim_cur); i++) {
+        memset(buf, 0, PATH_MAX);
+        memset(fd_path, 0, PATH_MAX);
+        sprintf(fd_path, "/proc/self/fd/%d", i);

[Daniel Erat, 2017/06/29 19:26:03]

snprintf

[teravest, 2017/06/29 19:50:25]

Done.

+        ssize_t count = readlink(fd_path, buf, PATH_MAX);

[Daniel Erat, 2017/06/29 19:26:03]

arraysize(buf)-1 instead of PATH_MAX here, i think (arraysize is generally
better when possible, and readlink doesn't append a null byte)

[teravest, 2017/06/29 19:50:25]

Done.

+        if (count >= 0) {
+          LOG(ERROR) << i << ": " << buf;
+        }
+      }
+
+      // TODO(teravest): Put fd information on the stack for breakpad.
+      CHECK(false) << "Logged for file descriptor exhaustion, crashing now";
+    }
+#endif  // defined(OS_CHROMEOS)
   }
   *readonly_mapped_file = readonly_fd.release();