[Xen-devel] [PATCH] blktap: fix blktapctrl abort

[Kouya Shimura <kouya@xxxxxxxxxxxxxx>]

On rebooting a hvm, the blktapctrl daemon has died.

gdb shows the following call trace:
(gdb) where
#0  0x00000039d1830155 in raise () from /lib64/libc.so.6
#1  0x00000039d1831bf0 in abort () from /lib64/libc.so.6
#2  0x00000039d186a38b in __libc_message () from /lib64/libc.so.6
#3  0x00000039d1871634 in _int_free () from /lib64/libc.so.6
#4  0x00000039d1874c5c in free () from /lib64/libc.so.6
#5  0x0000003320a01bdd in ueblktap_probe (h=0x6073b0, 
    w=<value optimized out>, bepath_im=<value optimized out>) at xenbus.c:270
#6  0x0000003320a020e0 in xs_fire_next_watch (h=0x6073b0) at 
xs_api.c:355
#7  0x0000000000401785 in main (argc=<value optimized out>, 
    argv=<value optimized out>) at blktapctrl.c:907

There is a case that "/local/domain/0/backend/tap/<dom_id>" exists but
"/local/domain/<dom_id>/vm" is not in the xenstore.


Signed-off-by: Kouya Shimura <kouya@xxxxxxxxxxxxxx>

diff -r c06732ac2392 tools/blktap/lib/xenbus.c
--- a/tools/blktap/lib/xenbus.c Thu Jan 21 15:13:00 2010 +0000
+++ b/tools/blktap/lib/xenbus.c Fri Jan 22 16:24:33 2010 +0900
@@ -232,8 +232,11 @@ static int check_sharing(struct xs_handl
                        ret = -1;
                        break;
                }
+               cur_dom_uuid = NULL;
                xs_gather(h, path, "vm", NULL, &cur_dom_uuid, NULL);
                free(path);
+               if (!cur_dom_uuid)
+                       continue;
 
                if (!strcmp(cur_dom_uuid, dom_uuid)) {
                        free(cur_dom_uuid);
@@ -256,8 +259,11 @@ static int check_sharing(struct xs_handl
                                ret = -1;
                                break;
                        }
+                       params = NULL;
                        xs_gather(h, path, "params", NULL, &params, NULL);
                        free(path);
+                       if (!params)
+                               continue;
 
                        image_path[1] = get_image_path(params);
                        if (!strcmp(image_path[0], image_path[1])) {

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