3 files changed, 59 insertions, 28 deletions
diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 0f9b406d8..ae33d14da 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -496,6 +496,7 @@ cc_binary(
     srcs = ["epoll.cc"],
     linkstatic = 1,
     deps = [
+        "//test/util:epoll_util",
         "//test/util:file_descriptor",
         "//test/util:posix_error",
         "//test/util:test_main",
@@ -844,6 +845,7 @@ cc_binary(
     srcs = ["inotify.cc"],
     linkstatic = 1,
     deps = [
+        "//test/util:epoll_util",
         "//test/util:file_descriptor",
         "//test/util:fs_util",
         "//test/util:temp_path",
@@ -852,6 +854,7 @@ cc_binary(
         "//test/util:thread_util",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/strings:str_format",
+        "@com_google_absl//absl/time",
     ],
 )
 
diff --git a/test/syscalls/linux/epoll.cc b/test/syscalls/linux/epoll.cc
index 9ae87c00b..46fba7b2d 100644
--- a/test/syscalls/linux/epoll.cc
+++ b/test/syscalls/linux/epoll.cc
@@ -25,6 +25,7 @@
 #include <unistd.h>
 
 #include "gtest/gtest.h"
+#include "test/util/epoll_util.h"
 #include "test/util/file_descriptor.h"
 #include "test/util/posix_error.h"
 #include "test/util/test_util.h"
@@ -37,18 +38,6 @@ namespace {
 constexpr int kFDsPerEpoll = 3;
 constexpr uint64_t kMagicConstant = 0x0102030405060708;
 
-// Returns a new epoll file descriptor.
-PosixErrorOr<FileDescriptor> NewEpollFD() {
-  // "Since Linux 2.6.8, the size argument is ignored, but must be greater than
-  // zero." - epoll_create(2)
-  int fd = epoll_create(/* size = */ 1);
-  MaybeSave();
-  if (fd < 0) {
-    return PosixError(errno, "epoll_create");
-  }
-  return FileDescriptor(fd);
-}
-
 // Returns a new eventfd.
 PosixErrorOr<FileDescriptor> NewEventFD() {
   int fd = eventfd(/* initval = */ 0, /* flags = */ 0);
@@ -59,22 +48,6 @@ PosixErrorOr<FileDescriptor> NewEventFD() {
   return FileDescriptor(fd);
 }
 
-// Registers `target_fd` with the epoll instance represented by `epoll_fd` for
-// the epoll events `events`. Events on `target_fd` will be indicated by setting
-// data.u64 to `data` in the returned epoll_event.
-PosixError RegisterEpollFD(int epoll_fd, int target_fd, int events,
-                           uint64_t data) {
-  struct epoll_event event;
-  event.events = events;
-  event.data.u64 = data;
-  int rc = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, target_fd, &event);
-  MaybeSave();
-  if (rc < 0) {
-    return PosixError(errno, "epoll_ctl");
-  }
-  return NoError();
-}
-
 uint64_t ms_elapsed(const struct timespec* begin, const struct timespec* end) {
   return (end->tv_sec - begin->tv_sec) * 1000 +
          (end->tv_nsec - begin->tv_nsec) / 1000000;
diff --git a/test/syscalls/linux/inotify.cc b/test/syscalls/linux/inotify.cc
index 0e361496c..167ca44a8 100644
--- a/test/syscalls/linux/inotify.cc
+++ b/test/syscalls/linux/inotify.cc
@@ -14,9 +14,12 @@
 
 #include <fcntl.h>
 #include <libgen.h>
+#include <sched.h>
+#include <sys/epoll.h>
 #include <sys/inotify.h>
 #include <sys/ioctl.h>
 
+#include <atomic>
 #include <list>
 #include <string>
 #include <vector>
@@ -24,6 +27,9 @@
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_format.h"
 #include "absl/strings/str_join.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+#include "test/util/epoll_util.h"
 #include "test/util/file_descriptor.h"
 #include "test/util/fs_util.h"
 #include "test/util/temp_path.h"
@@ -1512,6 +1518,55 @@ TEST(Inotify, ControlEvents) {
   ASSERT_THAT(events2, Are({}));
 }
 
+// Regression test to ensure epoll and directory access doesn't deadlock.
+TEST(Inotify, EpollNoDeadlock) {
+  const DisableSave ds;  // Too many syscalls.
+
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(InotifyInit1(IN_NONBLOCK));
+
+  // Create lots of directories and watch all of them.
+  const TempPath root = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  std::vector<TempPath> children;
+  for (size_t i = 0; i < 1000; ++i) {
+    auto child = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDirIn(root.path()));
+    ASSERT_NO_ERRNO_AND_VALUE(
+        InotifyAddWatch(fd.get(), child.path(), IN_ACCESS));
+    children.emplace_back(std::move(child));
+  }
+
+  // Run epoll_wait constantly in a separate thread.
+  std::atomic<bool> done(false);
+  ScopedThread th([&fd, &done] {
+    for (auto start = absl::Now(); absl::Now() - start < absl::Seconds(5);) {
+      FileDescriptor epoll_fd = ASSERT_NO_ERRNO_AND_VALUE(NewEpollFD());
+      ASSERT_NO_ERRNO(RegisterEpollFD(epoll_fd.get(), fd.get(),
+                                      EPOLLIN | EPOLLOUT | EPOLLET, 0));
+      struct epoll_event result[1];
+      EXPECT_THAT(RetryEINTR(epoll_wait)(epoll_fd.get(), result, 1, -1),
+                  SyscallSucceedsWithValue(1));
+
+      sched_yield();
+    }
+    done = true;
+  });
+
+  // While epoll thread is running, constantly access all directories to
+  // generate inotify events.
+  while (!done) {
+    std::vector<std::string> files =
+        ASSERT_NO_ERRNO_AND_VALUE(ListDir(root.path(), false));
+    ASSERT_EQ(files.size(), 1002);
+    for (const auto& child : files) {
+      if (child == "." || child == "..") {
+        continue;
+      }
+      ASSERT_NO_ERRNO_AND_VALUE(ListDir(JoinPath(root.path(), child), false));
+    }
+    sched_yield();
+  }
+}
+
 }  // namespace
 }  // namespace testing
 }  // namespace gvisor