lkml.org 
[lkml]   [2020]   [Mar]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH] ptp: free ptp clock properly
Hello, Andrea, all,

----- Original Message -----
> From: "Andrea Righi" <andrea.righi@canonical.com>
> Subject: [PATCH] ptp: free ptp clock properly
>
> There is a bug in ptp_clock_unregister() where ptp_clock_release() can
> free up resources needed by posix_clock_unregister() to properly destroy
> a related sysfs device.
>
> Fix this by calling posix_clock_unregister() in ptp_clock_release().

Honestly, this does not seem right. The calls at PTP clock release are:

ptp_clock_unregister() -> posix_clock_unregister() -> cdev_device_del() ->
-> ... bla ... -> ptp_clock_release()

So, it looks like with this patch both posix_clock_unregister() and
ptp_clock_release() are not called at all. And it looks like the "fix" is
not removing PTP clock's cdev, i.e. leaking it and related sysfs resources.

I would guess that a kernel in question (5.3.0-40-generic) has the commit
a33121e5487b but does not have the commit 75718584cb3c, which should be
exactly fixing a docking station disconnect crash. Could you please,
check this?

Why? We have 2 crash call traces. 1) the launchpad bug 2) the email which
led to the commit 75718584cb3c creation (see Link:).

Aaaaand they are identical starting from device_release_driver_internal()
and almost to the top.

> See also:
> commit 75718584cb3c ("ptp: free ptp device pin descriptors properly").
>
> BugLink: https://bugs.launchpad.net/bugs/1864754
> Fixes: a33121e5487b ("ptp: fix the race between the release of ptp_clock and
> cdev")
> Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
> ---
> drivers/ptp/ptp_clock.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
> index ac1f2bf9e888..12951023d0c6 100644
> --- a/drivers/ptp/ptp_clock.c
> +++ b/drivers/ptp/ptp_clock.c
> @@ -171,6 +171,7 @@ static void ptp_clock_release(struct device *dev)
> struct ptp_clock *ptp = container_of(dev, struct ptp_clock, dev);
>
> ptp_cleanup_pin_groups(ptp);
> + posix_clock_unregister(&ptp->clock);
> mutex_destroy(&ptp->tsevq_mux);
> mutex_destroy(&ptp->pincfg_mux);
> ida_simple_remove(&ptp_clocks_map, ptp->index);
> @@ -303,8 +304,6 @@ int ptp_clock_unregister(struct ptp_clock *ptp)
> if (ptp->pps_source)
> pps_unregister_source(ptp->pps_source);
>
> - posix_clock_unregister(&ptp->clock);
> -
> return 0;
> }
> EXPORT_SYMBOL(ptp_clock_unregister);
> --
> 2.25.0

Best regards,
Vladis Dronov | Red Hat, Inc. | The Core Kernel | Senior Software Engineer

\
 
 \ /
  Last update: 2020-03-04 21:12    [W:0.094 / U:4.892 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site