Add more detailed comments

1 files changed, 4 insertions, 2 deletions

diff --git a/src/core/lib/iomgr/ev_epoll1_linux.cc b/src/core/lib/iomgr/ev_epoll1_linux.cc
index 356fbae139..1c495b47bc 100644
--- a/src/core/lib/iomgr/ev_epoll1_linux.cc
+++ b/src/core/lib/iomgr/ev_epoll1_linux.cc
@@ -309,7 +309,9 @@ static grpc_fd* fd_create(int fd, const char* name, bool track_err) {
 
   struct epoll_event ev;
   ev.events = static_cast<uint32_t>(EPOLLIN | EPOLLOUT | EPOLLET);
-  /* Use the least significant bit of ev.data.ptr to store track_err. */
+  /* Use the least significant bit of ev.data.ptr to store track_err. We expect
+   * the addresses to be word aligned. We need to store track_err to avoid
+   * synchronization issues when accessing it after receiving an event. */
   ev.data.ptr = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(new_fd) |
                                         (track_err ? 1 : 0));
   if (epoll_ctl(g_epoll_set.epfd, EPOLL_CTL_ADD, fd, &ev) != 0) {
@@ -626,7 +628,7 @@ static grpc_error* process_epoll_events(grpc_pollset* pollset) {
       grpc_fd* fd = reinterpret_cast<grpc_fd*>(
           reinterpret_cast<intptr_t>(data_ptr) & ~static_cast<intptr_t>(1));
       bool track_err =
-          reinterpret_cast<intptr_t>(data_ptr) & ~static_cast<intptr_t>(1);
+          reinterpret_cast<intptr_t>(data_ptr) & static_cast<intptr_t>(1);
       bool cancel = (ev->events & EPOLLHUP) != 0;
       bool error = (ev->events & EPOLLERR) != 0;
       bool read_ev = (ev->events & (EPOLLIN | EPOLLPRI)) != 0;