mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-13 18:49:22 -04:00
819f7b88b4
In function nvmet_async_event_process() we only process AENs iff
there is an open slot on the ctrl->async_event_cmds[] && aen
event list posted by the target is not empty. This keeps host
posted AEN outstanding if target generated AEN list is empty.
We do cleanup the target generated entries from the aen list in
nvmet_ctrl_free()-> nvmet_async_events_free() but we don't
process AEN posted by the host. This leads to following problem :-
When processing admin sq at the time of nvmet_sq_destroy() holds
an extra percpu reference(atomic value = 1), so in the following code
path after switching to atomic rcu, release function (nvmet_sq_free())
is not getting called which blocks the sq->free_done in
nvmet_sq_destroy() :-
nvmet_sq_destroy()
percpu_ref_kill_and_confirm()
- __percpu_ref_switch_mode()
-- __percpu_ref_switch_to_atomic()
--- call_rcu() -> percpu_ref_switch_to_atomic_rcu()
---- /* calls switch callback */
- percpu_ref_put()
-- percpu_ref_put_many(ref, 1)
--- else if (unlikely(atomic_long_sub_and_test(nr, &ref->count)))
---- ref->release(ref); <---- Not called.
This results in indefinite hang:-
void nvmet_sq_destroy(struct nvmet_sq *sq)
...
if (ctrl && ctrl->sqs && ctrl->sqs[0] == sq) {
nvmet_async_events_process(ctrl, status);
percpu_ref_put(&sq->ref);
}
percpu_ref_kill_and_confirm(&sq->ref, nvmet_confirm_sq);
wait_for_completion(&sq->confirm_done);
wait_for_completion(&sq->free_done); <-- Hang here
Which breaks the further disconnect sequence. This problem seems to be
introduced after commit 64f5e9cdd7 ("nvmet: fix memory leak when
removing namespaces and controllers concurrently").
This patch processes ctrl->async_event_cmds[] in the admin sq destroy()
context irrespetive of aen_list. Also we get rid of the controller's
aen_list processing in the nvmet_sq_destroy() context and just ignore
ctrl->aen_list.
This results in nvmet_async_events_process() being called from workqueue
context so we adjust the code accordingly.
Fixes: 64f5e9cdd7 ("nvmet: fix memory leak when removing namespaces and controllers concurrently ")
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.