| From | Greg Kroah-Hartman <> | Subject | [ 020/171] SCSI: qla2xxx: Test and clear FCPORT_UPDATE_NEEDED atomically. | Date | Tue, 15 Jan 2013 14:43:05 -0800 |
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3.4-stable review patch. If anyone has any objections, please let me know.
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From: David Jeffery <djeffery@redhat.com>
commit a394aac88506159e047630fc90dc2242568382d8 upstream.
When the qla2xxx driver loses access to multiple, remote ports, there is a race condition which can occur which will keep the request stuck on a scsi request queue indefinitely.
This bad state occurred do to a race condition with how the FCPORT_UPDATE_NEEDED bit is set in qla2x00_schedule_rport_del(), and how it is cleared in qla2x00_do_dpc(). The problem port has its drport pointer set, but it has never been processed by the driver to inform the fc transport that the port has been lost. qla2x00_schedule_rport_del() sets drport, and then sets the FCPORT_UPDATE_NEEDED bit. In qla2x00_do_dpc(), the port lists are walked and any drport pointer is handled and the fc transport informed of the port loss, then the FCPORT_UPDATE_NEEDED bit is cleared. This leaves a race where the dpc thread is processing one port removal, another port removal is marked with a call to qla2x00_schedule_rport_del(), and the dpc thread clears the bit for both removals, even though only the first removal was actually handled. Until another event occurs to set FCPORT_UPDATE_NEEDED, the later port removal is never finished and qla2xxx stays in a bad state which causes requests to become stuck on request queues.
This patch updates the driver to test and clear FCPORT_UPDATE_NEEDED atomically. This ensures the port state changes are processed and not lost.
Signed-off-by: David Jeffery <djeffery@redhat.com> Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com> Signed-off-by: Saurav Kashyap <saurav.kashyap@qlogic.com> Signed-off-by: James Bottomley <JBottomley@Parallels.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/scsi/qla2xxx/qla_os.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/scsi/qla2xxx/qla_os.c +++ b/drivers/scsi/qla2xxx/qla_os.c @@ -3735,9 +3735,9 @@ qla2x00_do_dpc(void *data) "ISP abort end.\n"); } - if (test_bit(FCPORT_UPDATE_NEEDED, &base_vha->dpc_flags)) { + if (test_and_clear_bit(FCPORT_UPDATE_NEEDED, + &base_vha->dpc_flags)) { qla2x00_update_fcports(base_vha); - clear_bit(FCPORT_UPDATE_NEEDED, &base_vha->dpc_flags); } if (test_bit(ISP_QUIESCE_NEEDED, &base_vha->dpc_flags)) {
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