On 01/07/2011 01:37 AM, Max Matveev wrote:
I'm working with a customer who's getting the famous "scheduling while
atomic" noise in the logs when using his tape library connected via
iSCSI. The task is always an iscsi_q_31 and they're getting a lot of
those BUG messages.
I have the backtrace but it's almost useless - the code path is
unbelievable: the only reliable bit is
[<f8acca0e>] iscsi_tcp_segment_done+0x1c7/0x2a7 [libiscsi_tcp]
[<c05b7f45>] kernel_sendmsg+0x27/0x35
[<f8ad33e8>] iscsi_sw_tcp_pdu_xmit+0x9e/0x1e8 [iscsi_tcp]
[<f8acc246>] iscsi_tcp_task_xmit+0x25/0x204 [libiscsi_tcp]
[<f8d9b622>] iscsi_xmit_task+0x24/0x4b [libiscsi2]
[<f8d9c190>] iscsi_xmitworker+0x122/0x202 [libiscsi2]
If other people are hitting this try the attached patch.
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diff --git a/drivers/scsi/libiscsi_tcp.c b/drivers/scsi/libiscsi_tcp.c
index 8eeb39f..e98ae33 100644
--- a/drivers/scsi/libiscsi_tcp.c
+++ b/drivers/scsi/libiscsi_tcp.c
@@ -132,14 +132,25 @@ static void iscsi_tcp_segment_map(struct iscsi_segment
*segment, int recv)
if (page_count(sg_page(sg)) >= 1 && !recv)
return;
- segment->sg_mapped = kmap_atomic(sg_page(sg), KM_SOFTIRQ0);
+ if (recv) {
+ segment->atomic_mapped = true;
+ segment->sg_mapped = kmap_atomic(sg_page(sg), KM_SOFTIRQ0);
+ } else {
+ segment->atomic_mapped = false;
+ /* the xmit path can sleep with the page mapped so use kmap */
+ segment->sg_mapped = kmap(sg_page(sg));
+ }
+
segment->data = segment->sg_mapped + sg->offset + segment->sg_offset;
}
void iscsi_tcp_segment_unmap(struct iscsi_segment *segment)
{
if (segment->sg_mapped) {
- kunmap_atomic(segment->sg_mapped, KM_SOFTIRQ0);
+ if (segment->atomic_mapped)
+ kunmap_atomic(segment->sg_mapped, KM_SOFTIRQ0);
+ else
+ kunmap(sg_page(segment->sg));
segment->sg_mapped = NULL;
segment->data = NULL;
}
diff --git a/include/scsi/libiscsi_tcp.h b/include/scsi/libiscsi_tcp.h
index 741ae7e..e6b9fd2 100644
--- a/include/scsi/libiscsi_tcp.h
+++ b/include/scsi/libiscsi_tcp.h
@@ -47,6 +47,7 @@ struct iscsi_segment {
struct scatterlist *sg;
void *sg_mapped;
unsigned int sg_offset;
+ bool atomic_mapped;
iscsi_segment_done_fn_t *done;
};
