rs-preload: Handle recursive socket() calls

When ACM support is enabled in the librdmacm, it will attempt to
establish a socket connection to the ACM daemon.  When the rsocket
preload library is in use, this can result in a recursive call
to socket() that results in the library hanging.  The resulting
call stack is:

socket() -> rsocket() -> rdma_create_id() -> ucma_init() ->
socket() -> rsocket() -> rdma_create_id() -> ucma_init()

The second call to ucma_init() hangs because initialization is
still pending.

Fix this by checking for recursive calls to socket() in the preload
library.  When detected, call the real socket() call instead of
directing the call back into rsockets().  Since rsockets is a part
of the librdmacm, it can call rsockets directly if it wants to use
rsockets instead of standard sockets.

This problem and the cause was reported by Chet Murthy <chet@watson.ibm.com>

Signed-off-by: Sean Hefty <sean.hefty@intel.com>

diff --git a/src/preload.c b/src/preload.c
index a3ef48830cbf901841190feac658436cb2e1905c..d21389f37c5244ba2fa5b6149163e20d97211648 100644 (file)
--- a/src/preload.c
+++ b/src/preload.c
@@ -325,22 +325,28 @@ void set_rsocket_options(int rsocket)
 
 int socket(int domain, int type, int protocol)
 {
+       static __thread int recursive;
        int index, ret;
 
+       if (recursive)
+               goto real;
+
        init_preload();
        index = fd_open();
        if (index < 0)
                return index;
 
+       recursive = 1;
        ret = rsocket(domain, type, protocol);
+       recursive = 0;
        if (ret >= 0) {
                fd_store(index, ret, fd_rsocket);
                set_rsocket_options(ret);
                return index;
-       } else {
-               fd_close(index, &ret);
-               return real_socket(domain, type, protocol);
        }
+       fd_close(index, &ret);
+real:
+       return real_socket(domain, type, protocol);
 }
 
 int bind(int socket, const struct sockaddr *addr, socklen_t addrlen)