Il 11/05/2012 12:22, Ronnie Sahlberg ha scritto:
> Signed-off-by: Ronnie Sahlberg <ronniesahlb...@gmail.com>
> ---
> block/iscsi.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/block/iscsi.c b/block/iscsi.c
> index d37c4ee..989b5e9 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -105,7 +105,9 @@ iscsi_set_events(IscsiLun *iscsilun)
> {
> struct iscsi_context *iscsi = iscsilun->iscsi;
>
> - qemu_aio_set_fd_handler(iscsi_get_fd(iscsi), iscsi_process_read,
> + qemu_aio_set_fd_handler(iscsi_get_fd(iscsi),
> + (iscsi_queue_length(iscsi) > 0)
> + ? iscsi_process_read : NULL,
> (iscsi_which_events(iscsi) & POLLOUT)
> ? iscsi_process_write : NULL,
> iscsi_process_flush, iscsilun);
I wonder if iscsi is also susceptible to the same race condition I saw
with NBD, where you can have:
1) select in the iothread exiting and reporting readability
2) the iothread subsequently blocking on the mutex
3) a VCPU thread's qemu_aio_wait() calling iscsi_process_read
4) when the VCPU releases the mutex, the iothread will call
iscsi_process_read again.
This should be easily reproducible with IDE drives, but the above patch
would not fix it. Perhaps it's better to call iscsi_queue_length in
iscsi_process_read instead.
Paolo
