On Fri, Jan 31, 2020 at 3:38 PM Janne Blomqvist
<blomqvist.ja...@gmail.com> wrote:
>
> Simplify IO locking in libgfortran. The new IO implementation avoids
> accessing units without locks, as seen in PR 92836. It also avoids
> lock inversion (except for a corner case wrt namelist query when
> reading from stdin and outputting to stdout), making it easier to
> verify correctness with tools like valgrind or threadsanitizer. It is
> also simplified as the waiting and closed variables are not needed
> anymore, making it easier to understand and analyze.
>
> Regtested on x86_64-pc-linux-gnu, Ok for master?
And, I forgot the ChangeLog entry. Here it is:
libgfortran/ChangeLog:
2020-01-31 Janne Blomqvist <j...@gcc.gnu.org>
PR libfortran/92836
* io/close.c (st_close): Close unit with unit_lock held.
* io/io.h (gfc_unit): Remove waiting and closed members.
(find_unit_locked): New prototype.
(inc_waiting_locked): Remove.
(predec_waiting_locked): Remove.
(dec_waiting_unlocked): Remove.
* io/list_read.c (nml_query): Avoid deadlock due to lock
inversion.
* io/unit.c (newunit_lock): New variable.
(get_gfc_unit): Add new argument, use it. Remove logic waiting for
closing logic..
(find_unit): Use new argument for get_gfc_unit.
(find_unit_locked): New function.
(find_or_create_unit): Use new argumet for gfc_get_unit.
(get_unit): Likewise.
(init_units): Initialize newunit_lock.
(close_unit_1): Change meaning of locked argument, remove waiting
for closing logic.
(close_unit): Adapt to new close_unit_1 arguments.
(close_units): Likewwise.
(newunit_alloc): Use newunit_lock to protect.
(newunit_free): Likewise.
* io/unix.c (find_file0): Lock unit before accessing.
(find_file): Remove waiting for closing logic.
(flush_all_units_1): Likewise.
(flush_all_units): Likewise.
--
Janne Blomqvist
