[PATCH] xen/manage: Fix suspend error path

[Lukas Wunner <lukas@xxxxxxxxx>]

The device power management API has the following asymmetry:
* dpm_suspend_start() does not clean up on failure
  (it requires a call to dpm_resume_end())
* dpm_suspend_end() does clean up on failure
  (it does not require a call to dpm_resume_start())

The asymmetry was introduced by commit d8f3de0d2412 ("Suspend-related
patches for 2.6.27") in June 2008:  It removed a call to device_resume()
from device_suspend() (which was later renamed to dpm_suspend_start()).

When Xen began using the device power management API in May 2008 with
commit 0e91398f2a5d ("xen: implement save/restore"), the asymmetry did
not yet exist.  But since it was introduced, a call to dpm_resume_end()
is missing in the error path of dpm_suspend_start().  Fix it.

Fixes: d8f3de0d2412 ("Suspend-related patches for 2.6.27")
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx  # v2.6.27
---
kexec suffered from the same issue ever since it began using the
device power management API in July 2008 with commit 89081d17f7bb
("kexec jump: save/restore device state").  It was fixed this year
by commit 996afb6efd1a ("kexec_core: Fix error code path in the
KEXEC_JUMP flow").  All other callers seem fine.

 drivers/xen/manage.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index 841afa4..1f5a7a4 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -110,7 +110,7 @@ static void do_suspend(void)
        err = dpm_suspend_start(PMSG_FREEZE);
        if (err) {
                pr_err("%s: dpm_suspend_start %d\n", __func__, err);
-               goto out_thaw;
+               goto out_resume_end;
        }
 
        printk(KERN_DEBUG "suspending xenstore...\n");
@@ -150,6 +150,7 @@ static void do_suspend(void)
        else
                xs_suspend_cancel();
 
+out_resume_end:
        dpm_resume_end(si.cancelled ? PMSG_THAW : PMSG_RESTORE);
 
 out_thaw:
-- 
2.50.1