Re: [Tarantool-patches] [PATCH luajit v2 5/7] core: introduce memory profiler

[Sergey Kaplun <skaplun@tarantool.org>]

Hi, Sergos!

Thanks for the review!

On 27.12.20, Sergey Ostanevich wrote:
> Hi!
> 
> Thanks for the patch! Just one question below, looks good otherwise.
> 
> Sergos
> 
> > diff --git a/src/lj_memprof.c b/src/lj_memprof.c
> > new file mode 100644
> > index 0000000..e0df057
> > --- /dev/null
> > +++ b/src/lj_memprof.c
> <snipped>
> > +static int memprof_stop(const struct lua_State *L)
> > +{
> > +  struct memprof *mp = &memprof;
> > +  struct alloc *oalloc = &mp->orig_alloc;
> > +  struct lj_wbuf *out = &mp->out;
> > +  int return_status = PROFILE_SUCCESS;
> > +  int saved_errno = 0;
> > +  struct lua_State *main_L;
> > +  int cb_status;
> > +
> > +  memprof_lock();
> > +
> > +  if (mp->state == MPS_HALT) {
> > +    errno = mp->saved_errno;
> > +    mp->state = MPS_IDLE
> > +    memprof_unlock();
> > +    return PROFILE_ERRIO;
> > +  }
> > +
> > +  if (mp->state != MPS_PROFILE) {
> > +    memprof_unlock();
> > +    return PROFILE_ERRRUN;
> > +  }
> > +
> 
> > +  if (L != NULL && mp->g != G(L)) {
> > +    memprof_unlock();
> > +    return PROFILE_ERR;
> > +  }
> > +
> > +  mp->state = MPS_IDLE;
> > +
> > +  lua_assert(mp->g != NULL);
> > +  main_L = mainthread(mp->g);
> > +
> > +  lua_assert(memprof_allocf == lua_getallocf(main_L, NULL));
> > +  lua_assert(oalloc->allocf != NULL);
> > +  lua_assert(oalloc->state != NULL);
> > +  lua_setallocf(main_L, oalloc->allocf, oalloc->state);
> > +
> > +  if (LJ_UNLIKELY(lj_wbuf_test_flag(out, STREAM_STOP))) {
> > +    lua_assert(lj_wbuf_test_flag(out, STREAM_ERR_IO));
> > +    mp->state = MPS_HALT;
> > +    /* on_stop call may change errno value. */
> > +    mp->saved_errno = lj_wbuf_errno(out);
> > +    /* Ignore possible errors. mp->opt.buf == NULL here. */
> > +    mp->opt.on_stop(mp->opt.ctx, mp->opt.buf);
> > +    lj_wbuf_terminate(out);
> > +    memprof_unlock();
> > +    return PROFILE_ERRIO;
> > +  }
> > +  lj_wbuf_addbyte(out, LJM_EPILOGUE_HEADER);
> > +
> > +  lj_wbuf_flush(out);
> > +
> > +  cb_status = mp->opt.on_stop(mp->opt.ctx, mp->opt.buf);
> > +  if (LJ_UNLIKELY(lj_wbuf_test_flag(out, STREAM_ERR_IO) || cb_status != 0)) {
> > +    saved_errno = lj_wbuf_errno(out);
> 
> Previous return of PROFILE_ERRIO causes MPS_HALT. Should it be the same?

Yes, you're right! Previous MPS_HALT is redundant -- profiler anyway
should stop (IDLE) immediately, there is no reason to set HALT there.
Thanks! Fixed!

See the iterative diff below. Branch is force-pushed.

> 
> > +    return_status = PROFILE_ERRIO;
> > +  }
> > +
> > +  lj_wbuf_terminate(out);
> > +
> > +  memprof_unlock();
> > +  errno = saved_errno;
> > +  return return_status;
> > +}
> 

===================================================================
diff --git a/src/lj_memprof.c b/src/lj_memprof.c
index e0df057..998cbea 100644
--- a/src/lj_memprof.c
+++ b/src/lj_memprof.c
@@ -354,13 +354,13 @@ static int memprof_stop(const struct lua_State *L)
 
   if (LJ_UNLIKELY(lj_wbuf_test_flag(out, STREAM_STOP))) {
     lua_assert(lj_wbuf_test_flag(out, STREAM_ERR_IO));
-    mp->state = MPS_HALT;
     /* on_stop call may change errno value. */
-    mp->saved_errno = lj_wbuf_errno(out);
+    saved_errno = lj_wbuf_errno(out);
     /* Ignore possible errors. mp->opt.buf == NULL here. */
     mp->opt.on_stop(mp->opt.ctx, mp->opt.buf);
     lj_wbuf_terminate(out);
     memprof_unlock();
+    errno = saved_errno;
     return PROFILE_ERRIO;
   }
   lj_wbuf_addbyte(out, LJM_EPILOGUE_HEADER);
===================================================================

-- 
Best regards,
Sergey Kaplun