diff options
| -rw-r--r-- | test/nptl/tst-cancel4.c | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/test/nptl/tst-cancel4.c b/test/nptl/tst-cancel4.c index e7119589f..53abf83ee 100644 --- a/test/nptl/tst-cancel4.c +++ b/test/nptl/tst-cancel4.c @@ -83,7 +83,30 @@ static pthread_barrier_t b2; # define IPC_ADDVAL 0 #endif -#define WRITE_BUFFER_SIZE 4096 +/* The WRITE_BUFFER_SIZE value needs to be chosen such that if we set + the socket send buffer size to '1', a write of this size on that + socket will block. + + The Linux kernel imposes a minimum send socket buffer size which + has changed over the years. As of Linux 3.10 the value is: + + 2 * (2048 + SKB_DATA_ALIGN(sizeof(struct sk_buff))) + + which is attempting to make sure that with standard MTUs, + TCP can always queue up at least 2 full sized packets. + + Furthermore, there is logic in the socket send paths that + will allow one more packet (of any size) to be queued up as + long as some socket buffer space remains. Blocking only + occurs when we try to queue up a new packet and the send + buffer space has already been fully consumed. + + Therefore we must set this value to the largest possible value of + the formula above (and since it depends upon the size of "struct + sk_buff", it is dependent upon machine word size etc.) plus some + slack space. */ + +#define WRITE_BUFFER_SIZE 16384 /* Cleanup handling test. */ static int cl_called; @@ -758,7 +781,6 @@ tf_sigpause (void *arg) pthread_cleanup_push (cl, NULL); - /* Just for fun block the cancellation signal. */ sigpause (SIGCANCEL); pthread_cleanup_pop (0); |