Re: [Libguestfs] [libnbd PATCH] tests: Enhance errors test
On Thu, Jun 27, 2019 at 10:18:30PM -0500, Eric Blake wrote:
+ /* Queue up a write command so large that we block on POLLIN, then
queue
+ * multiple disconnects. XXX The last one should fail.
+ */
+ if (nbd_aio_pwrite (nbd, buf, 2 * 1024 * 1024, 0, 0) == -1) {
+ fprintf (stderr, "%s: %s\n", argv[0], nbd_get_error ());
+ exit (EXIT_FAILURE);
+ }
+ if ((nbd_aio_get_direction (nbd) & LIBNBD_AIO_DIRECTION_WRITE) == 0) {
+ fprintf (stderr, "%s: test failed: "
+ "expect to be blocked on write\n",
+ argv[0]);
+ exit (EXIT_FAILURE);
+ }
This test fails when run under valgrind. An abbreviated log shows
what's happening:
libnbd: debug: nbd_aio_pwrite: event CmdIssue: READY -> ISSUE_COMMAND.START
libnbd: debug: nbd_aio_pwrite: transition: ISSUE_COMMAND.START -> ISSUE_COMMAND.
SEND_REQUEST
libnbd: debug: nbd_aio_pwrite: transition: ISSUE_COMMAND.SEND_REQUEST -> ISSUE_C
OMMAND.PREPARE_WRITE_PAYLOAD
libnbd: debug: nbd_aio_pwrite: transition: ISSUE_COMMAND.PREPARE_WRITE_PAYLOAD -
ISSUE_COMMAND.SEND_WRITE_PAYLOAD
libnbd: debug: nbd_aio_pwrite:
transition: ISSUE_COMMAND.SEND_WRITE_PAYLOAD -> I
SSUE_COMMAND.FINISH
libnbd: debug: nbd_aio_pwrite: transition: ISSUE_COMMAND.FINISH -> READY
/home/rjones/d/libnbd/tests/.libs/lt-errors: test failed: expect to be blocked on write
It seems as if this is caused by valgrinded code running more slowly,
rather than an actual valgrind/memory error.
I wonder if we could remove the race using a custom nbdkit-sh-plugin
which would block on writes until (eg) a local trigger file was
touched? Even that seems as if it would depend on the amount of data
that the kernel is able to buffer.
Rich.
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