re: port-mips/52892: Tests hang on MIPS

[matthew green <mrg%eterna.com.au@localhost>]

The following reply was made to PR port-mips/52892; it has been noted by GNATS.

From: matthew green <mrg%eterna.com.au@localhost>
To: christos%zoulas.com@localhost (Christos Zoulas)
Cc: port-mips-maintainer%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
    netbsd-bugs%netbsd.org@localhost, gson%gson.org@localhost (Andreas Gustafsson),
    gnats-bugs%NetBSD.org@localhost
Subject: re: port-mips/52892: Tests hang on MIPS
Date: Mon, 23 Apr 2018 07:11:40 +1000

 > | >  Index: kern_condvar.c
 > | >  =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
 > | >  RCS file: /cvsroot/src/sys/kern/kern_condvar.c,v
 > | >  retrieving revision 1.41
 > | >  diff -u -r1.41 kern_condvar.c
 > | >  --- kern_condvar.c	30 Jan 2018 07:52:22 -0000	1.41
 > | >  +++ kern_condvar.c	22 Apr 2018 16:12:19 -0000
 > | >  @@ -268,9 +268,10 @@
 > | >   =
 
 > | >   	KASSERT(mutex_owned(mtx));
 > | >   =
 
 > | >  -	cv_enter(cv, mtx, l);
 > | >  +	CV_LOCKDEBUG_HANDOFF(l, cv);
 > | >   	error =3D sleepq_block(0, true);
 > | >  -	return cv_exit(cv, mtx, l, error);
 > | >  +	mutex_enter(mtx);
 > | >  +	return error;
 > | >   }
 > | =
 
 > | this can't be right.  you've removed cv_enter() entirely,
 > | and the cv_exit() only means we don't potentially cv_signal()
 > | something.  perhaps this is proc_lock being held issue, ie,
 > | is that the only place it could hang here?
 > =
 
 > Then cv_wait() is wrong too, because it is the same code; except sleepq_=
 block
 > is called with false.
 
 what cv_wait() are you looking at?  mine shows:
 
 235 void
 236 cv_wait(kcondvar_t *cv, kmutex_t *mtx)
 237 {
 238         lwp_t *l =3D curlwp;
 239
 240         KASSERT(mutex_owned(mtx));
 241
 242         cv_enter(cv, mtx, l);
 243
 244         /*
 245          * We can't use cv_exit() here since the cv might be destroyed=
  before
 246          * this thread gets a chance to run.  Instead, hand off the lo=
 ckdebug
 247          * responsibility to the thread that wakes us up.
 248          */
 249
 250         CV_LOCKDEBUG_HANDOFF(l, cv);
 251         (void)sleepq_block(0, false);
 252         mutex_enter(mtx);
 253 }
 
 note L242.
 
 did you actually test this change? :)
 
 
 .mrg.