Re: [Tarantool-patches] [PATCH luajit v3 2/2] misc: add Lua API for memory profiler

[Sergey Kaplun <skaplun@tarantool.org>]

Igor,

Thanks for the review!

On 28.12.20, Igor Munkin wrote:
> Sergey,
> 
> Thanks for the patch! LGTM with the several comments below.
> 
> On 28.12.20, Sergey Kaplun wrote:
> > This patch introduces Lua API for LuaJIT memory profiler implemented in
> > the scope of the previous patch.
> > 
> > Profiler returns true value if started/stopped successfully,
> > returns nil on failure (plus an error message as a second result and a
> > system-dependent error code as a third result).
> > If LuaJIT is build without memory profiler both return `false`.
> 
> Typo: s/`false`/false/ considering true and nil above.

Done.

> 
> > 
> > <lj_errmsg.h> have adjusted with three new errors
> 
> Typo: s/have adjusted/has been adjusted/.

Fixed.

> 
> > PROF_MISUSE/PROF_ISRUNNING/PROF_NOTRUNNING returned in case when
> > profiler has used incorrectly/started/stopped already correspondingly.
> > 
> > Part of tarantool/tarantool#5442
> > ---
> > 
> > Changes in v3:
> >   * Fixed lj_mem_new misuse.
> >   * Moved buffer inside ctx.
> >   * Codestyle fixes.
> > 
> >  src/Makefile.dep |   5 +-
> >  src/lib_misc.c   | 166 +++++++++++++++++++++++++++++++++++++++++++++++
> >  src/lj_errmsg.h  |   7 ++
> >  3 files changed, 176 insertions(+), 2 deletions(-)
> > 
> 
> <snipped>
> 
> > diff --git a/src/lib_misc.c b/src/lib_misc.c
> > index 6f7b9a9..619cfb7 100644
> > --- a/src/lib_misc.c
> > +++ b/src/lib_misc.c
> 
> <snipped>
> 
> > @@ -67,8 +75,166 @@ LJLIB_CF(misc_getmetrics)
> 
> <snipped>
> 
> > +/* local started, err, errno = misc.memprof.start(fname) */
> > +LJLIB_CF(misc_memprof_start)
> > +{
> 
> <snipped>
> 
> > +  if (LJ_UNLIKELY(memprof_status != PROFILE_SUCCESS)) {
> > +    lj_mem_free(ctx->g, ctx, sizeof(*ctx));
> 
> This deallocation causes double free if PROFILE_ERRIO occurs, since the
> ctx is released within on_stop callback.
> 
> ctx->stream should be closed if PROFILE_ERR(USE|RUN) occurs.

This is the reason why I suggested not to call on_stop callback on
finish -- this "corner case" looks weird.
Nice catch! See the iterative patch below.

> 
> > +    switch (memprof_status) {
> 
> <snipped>
> 
> > +    }
> > +  }
> > +  lua_pushboolean(L, 1);
> > +
> 
> Typo: Excess newline.

Fixed.

> 
> > +  return 1;
> > +}
> 
> <snipped>
> 
> > -- 
> > 2.28.0
> > 
> 
> -- 
> Best regards,
> IM

===================================================================
diff --git a/src/lib_misc.c b/src/lib_misc.c
index 619cfb7..958c189 100644
--- a/src/lib_misc.c
+++ b/src/lib_misc.c
@@ -177,7 +177,10 @@ LJLIB_CF(misc_memprof_start)
   memprof_status = lj_memprof_start(L, &opt);
 
   if (LJ_UNLIKELY(memprof_status != PROFILE_SUCCESS)) {
-    lj_mem_free(ctx->g, ctx, sizeof(*ctx));
+    if (memprof_status == PROFILE_ERRIO) {
+      fclose(ctx->stream);
+      lj_mem_free(ctx->g, ctx, sizeof(*ctx));
+    }
     switch (memprof_status) {
     case PROFILE_ERRUSE:
       lua_pushnil(L);
@@ -197,7 +200,6 @@ LJLIB_CF(misc_memprof_start)
     }
   }
   lua_pushboolean(L, 1);
-
   return 1;
 }
===================================================================

-- 
Best regards,
Sergey Kaplun