# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1201001620 0
# Node ID 89b51e83577169bda9f7db8bfb9c63a04e19672f
# Parent b2cb82c753ce3d8dd7e949d0d59ed7d1edb448ac
blkback/blktap: Check for kthread_should_stop() in inner loop,
mdelaay() should be msleep(), and these changes belong in blktap as
well as blkback.
Based on comments and patches from Jan Beulich and Steven Smith.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
linux-2.6.18-xen changeset: 392:7070d34f251c3e0c411022a5d365aea9804114a7
linux-2.6.18-xen date: Mon Jan 21 11:43:31 2008 +0000
blkback: Request-processing loop is unbounded and hence requires a
yield point. Also, bad request type is a good cause to sleep for a
short while as the frontend has probably gone mad.
Patch by Steven Smith <steven.smith@xxxxxxxxxxxxx>
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
linux-2.6.18-xen changeset: 391:77f831cbb91ddca3a7539fa9197d4abc2d2bfcf9
linux-2.6.18-xen date: Fri Jan 18 16:52:25 2008 +0000
---
linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c | 18 ++++++++++++++++--
linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c | 15 ++++++++++++++-
2 files changed, 30 insertions(+), 3 deletions(-)
diff -r b2cb82c753ce -r 89b51e835771
linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c
--- a/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c Tue Jan 22
11:32:49 2008 +0000
+++ b/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c Tue Jan 22
11:33:40 2008 +0000
@@ -38,6 +38,7 @@
#include <linux/spinlock.h>
#include <linux/kthread.h>
#include <linux/list.h>
+#include <linux/delay.h>
#include <xen/balloon.h>
#include <asm/hypervisor.h>
#include "common.h"
@@ -311,7 +312,7 @@ static int do_block_io_op(blkif_t *blkif
rp = blk_rings->common.sring->req_prod;
rmb(); /* Ensure we see queued requests up to 'rp'. */
- while ((rc != rp)) {
+ while (rc != rp) {
if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
break;
@@ -319,6 +320,11 @@ static int do_block_io_op(blkif_t *blkif
pending_req = alloc_req();
if (NULL == pending_req) {
blkif->st_oo_req++;
+ more_to_do = 1;
+ break;
+ }
+
+ if (kthread_should_stop()) {
more_to_do = 1;
break;
}
@@ -351,6 +357,9 @@ static int do_block_io_op(blkif_t *blkif
dispatch_rw_block_io(blkif, &req, pending_req);
break;
default:
+ /* A good sign something is wrong: sleep for a while to
+ * avoid excessive CPU consumption by a bad guest. */
+ msleep(1);
DPRINTK("error: unknown block io operation [%d]\n",
req.operation);
make_response(blkif, req.id, req.operation,
@@ -358,7 +367,11 @@ static int do_block_io_op(blkif_t *blkif
free_req(pending_req);
break;
}
- }
+
+ /* Yield point for this unbounded loop. */
+ cond_resched();
+ }
+
return more_to_do;
}
@@ -509,6 +522,7 @@ static void dispatch_rw_block_io(blkif_t
fail_response:
make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR);
free_req(pending_req);
+ msleep(1); /* back off a bit */
}
diff -r b2cb82c753ce -r 89b51e835771
linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c
--- a/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c Tue Jan 22 11:32:49
2008 +0000
+++ b/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c Tue Jan 22 11:33:40
2008 +0000
@@ -52,6 +52,7 @@
#include <linux/major.h>
#include <linux/gfp.h>
#include <linux/poll.h>
+#include <linux/delay.h>
#include <asm/tlbflush.h>
#define MAX_TAP_DEV 256 /*the maximum number of tapdisk ring devices */
@@ -1242,6 +1243,11 @@ static int do_block_io_op(blkif_t *blkif
break;
}
+ if (kthread_should_stop()) {
+ more_to_do = 1;
+ break;
+ }
+
switch (blkif->blk_protocol) {
case BLKIF_PROTOCOL_NATIVE:
memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc),
@@ -1270,6 +1276,9 @@ static int do_block_io_op(blkif_t *blkif
break;
default:
+ /* A good sign something is wrong: sleep for a while to
+ * avoid excessive CPU consumption by a bad guest. */
+ msleep(1);
WPRINTK("unknown operation [%d]\n",
req.operation);
make_response(blkif, req.id, req.operation,
@@ -1277,6 +1286,9 @@ static int do_block_io_op(blkif_t *blkif
free_req(pending_req);
break;
}
+
+ /* Yield point for this unbounded loop. */
+ cond_resched();
}
blktap_kick_user(blkif->dev_num);
@@ -1503,7 +1515,8 @@ static void dispatch_rw_block_io(blkif_t
fail_response:
make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR);
free_req(pending_req);
-}
+ msleep(1); /* back off a bit */
+}
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