On 2024/1/3 19:12, Tobias Burnus wrote:
On 22.12.23 03:36, Lipeng Zhu wrote:
This patch try to fix the bug when HAVE_ATOMIC_FETCH_ADD is
not defined in dec_waiting_unlocked function.

libgfortran/ChangeLog:

      * io/io.h (dec_waiting_unlocked): Use
      __gthread_rwlock_wrlock/__gthread_rwlock_unlock or
      __gthread_mutex_lock/__gthread_mutex_unlock functions
      to replace WRLOCK and RWUNLOCK macros.

Signed-off-by: Lipeng Zhu <lipeng....@intel.com>

The change looks good to me + I assume it will work, but have not tested
it myself.

Downside is that it slightly breaks with the abstraction done with all
the macros, but it seems to be the simplest solution.


Hi Tobias,

Thanks for your review, the reason I changed like this is because I found when LOCK macro was first introduced in this patch: https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=2b4c90656132abb8b8ad155d345c7d4fbf1687c9, it replaced __gthread_mutex_lock method with LOCK macro in other files like io/unit.c, but remained __gthread_mutex_lock in io/io.h. I am not sure if this is intentional or not, to avoid potential risk, I used the most straightforward solution.


What is really missing - and should be included in the commit message
(before the ChangeLog block) - is the following information:

    As io.h does not include async.h, the WRLOCK and RWUNLOCK macros are
undefined.

(Or something similar in other words.)

I think that helps others when looking at "git log" and wondering *why*
that change was needed.

Thanks,

Tobias


Thanks, I will update the commit message as suggested.

Lipeng Zhu

  libgfortran/io/io.h | 10 ++++++++--
  1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/libgfortran/io/io.h b/libgfortran/io/io.h
index 15daa0995b1..c7f0f7d7d9e 100644
--- a/libgfortran/io/io.h
+++ b/libgfortran/io/io.h
@@ -1020,9 +1020,15 @@ dec_waiting_unlocked (gfc_unit *u)
  #ifdef HAVE_ATOMIC_FETCH_ADD
    (void) __atomic_fetch_add (&u->waiting, -1, __ATOMIC_RELAXED);
  #else
-  WRLOCK (&unit_rwlock);
+#ifdef __GTHREAD_RWLOCK_INIT
+  __gthread_rwlock_wrlock (&unit_rwlock);
+  u->waiting--;
+  __gthread_rwlock_unlock (&unit_rwlock);
+#else
+  __gthread_mutex_lock (&unit_rwlock);
    u->waiting--;
-  RWUNLOCK (&unit_rwlock);
+  __gthread_mutex_unlock (&unit_rwlock);
+#endif
  #endif
  }
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