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pps: generators: stop the generator on unregister

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Both generator drivers stop their timer and then call
pps_gen_unregister_source(): pps_gen_tio_remove() cancels its hrtimer
and disables the TIO, and pps_gen_dummy_exit() deletes its timer. But
/dev/pps-genN and the sysfs "enable" attribute are still there until
the unregister, and a PPS_GEN_SETENABLE or a write to "enable" in
between starts the timer again. Nothing stops it after that: TIO's
hrtimer keeps running in the devm memory freed by the unbind, and the
dummy's timer is left in the unloaded module.

The drivers can't avoid this by unregistering first, as TIO's timer
callback uses pps_gen, which the unregister may free.

Stop the generator in pps_gen_unregister_cdev() instead, under
info_lock after the device and its sysfs files are gone, when nothing
can enable it again. pps_gen_unregister_source() then also does what
its kernel-doc says: "it disables the generator so no pulses are
generated anymore".

Fixes: 86b525bed2 ("drivers pps: add PPS generators support")
Cc: stable@vger.kernel.org
Suggested-by: Rodolfo Giometti <giometti@enneenne.com>
Assisted-by: LLM
Signed-off-by: Danish Khateeb <danishkhateeb03@gmail.com>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Link: https://patch.msgid.link/20260929124937.51114-4-danishkhateeb03@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Danish Khateeb 2026-09-29 07:49:36 -05:00 committed by Greg Kroah-Hartman
parent 4e8063cae3
commit 3e75af9f41
1 changed files with 10 additions and 1 deletions
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11
drivers/pps/generators/pps_gen.c
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@ -228,9 +228,18 @@ static void pps_gen_unregister_cdev(struct pps_gen_device *pps_gen)
* An open file keeps pps_gen around, but the driver may free info as
* soon as we return. The sysfs files are gone now, so wait for the
* ioctls using info and make later ones fail.
*
* The driver may have stopped the generator before calling us, but
* userspace could have enabled it again since. Nothing can enable it
* after this point, so stop it here for good.
*/
scoped_guard(mutex, &pps_gen->info_lock)
scoped_guard(mutex, &pps_gen->info_lock) {
if (pps_gen->enabled) {
pps_gen->info->enable(pps_gen, false);
pps_gen->enabled = false;
}
pps_gen->info = NULL;
}
put_device(&pps_gen->dev);
}