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authorDavid S. Miller <davem@davemloft.net>2013-07-23 02:31:37 -0700
committerDavid S. Miller <davem@davemloft.net>2013-07-23 02:31:37 -0700
commite7074e4c5edb0acaa979ea08e533736f906a9d68 (patch)
tree05d6ef7fb250464b8a46d556376f334c03c770a6
parent1fe2988f523ddbad93ca7abc98fea982f2ae0505 (diff)
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Increase nptl test case buffer size so we really block on current Linux kernels.
* tst-cancel4.c (WRITE_BUFFER_SIZE): Increase to 16384.
-rw-r--r--nptl/ChangeLog4
-rw-r--r--nptl/tst-cancel4.c25
2 files changed, 28 insertions, 1 deletions
diff --git a/nptl/ChangeLog b/nptl/ChangeLog
index fc2ef41a94c..0e4747e789b 100644
--- a/nptl/ChangeLog
+++ b/nptl/ChangeLog
@@ -1,3 +1,7 @@
+2013-07-22 David S. Miller <davem@davemloft.net>
+
+ * tst-cancel4.c (WRITE_BUFFER_SIZE): Increase to 16384.
+
2013-07-19 Dominik Vogt <vogt@de.ibm.com>
* pthread_mutex_lock.c: Fix whitespace.
diff --git a/nptl/tst-cancel4.c b/nptl/tst-cancel4.c
index 9ffd5d1419a..10b7c6e1b0e 100644
--- a/nptl/tst-cancel4.c
+++ b/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 choosen 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. Currently 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;