@@ -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);
Test on Linux 3.16.1 in Qemu ARM fails with: TEST_EXEC nptl/ tst-cancel4 ret == 1 ; expected_ret == 0 make[1]: *** [tst-cancel4.exe] Error 1 The output of failed test is: minimum write buffer size too large ../Test.mak:89: recipe for target 'tst-cancel4.exe' failed Signed-off-by: Waldemar Brodkorb <wbx@openadk.org> --- test/nptl/tst-cancel4.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-)