On Thu, Sep 4, 2025 at 3:11 PM Lukas Wunner <lu...@wunner.de> wrote:
>
> 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 <lu...@wunner.de>
> Cc: sta...@vger.kernel.org # v2.6.27
Thanks for catching this!
Reviewed-by: Rafael J. Wysocki (Intel) <raf...@kernel.org>
> ---
> 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
>
>
