On 30 Dec 2020, at 12:06, Igor Munkin <imun@tarantool.org> wrote:

Sergey,

Thanks for the patch! LGTM except the wording in commit message
(consider the comments below).

Side note: I want to notice that with on_start callback things would be
clearer. Let's return to this again later.

On 30.12.20, Sergey Kaplun wrote:

When the profiler is failing to start with error different from

Typo: s/is failing/fails/.
Typo: s/with error/with the error/.

PROFILE_ERRIO neither a file stream is closed nor ctx is freed
in case of incorrect return status checking.

Strictly saying there are two problems:
* Possible leakage for PROFILE_ERRRUN
* Double free for PROFILE_ERRIO

So I propose the following wording:

| When memory profiler fails to start with PROFILE_ERRRUN status both
| stream and ctx are not released. At the same time when memory profiler
| fails to start with the PROFILE_ERRIO status both stream and ctx are
| released twice. Both cases occur due to invalid return status checking.

To avoid this behaviour on_stop callback is called manually inside

Minor: s/To avoid this behaviour/To fix the leakage/.

the profiler when error on start is occurring. Checks in

Typo: s/is occuring/occurs/.

misc.memprof.start() are omitted.

Follows up tarantool/tarantool#5442
---

* How patch was checked:
Before patch you can occur the error like:
| $ src/luajit -e '
| local f, msg, errno = misc.memprof.start("/tmp/tmp_memprofile.bin")
| misc.memprof.start("/tmp/tmp_memprofile.bin") print(f,msg,errno)
| '
| true    nil     nil
| luajit: lj_state.c:178: close_state: Assertion `g->gc.total == sizeof(GG_State)' failed.
This patch fixes it.

* Why this assertion is not failed in tests (we have the test with same
functionality)?
This assertion failed inside close_state. Tarantool in some reason
doesn't call lua_close on stop. It's weird to me. I'll try to find an
explanation and will create a ticket.

* Why I don't create a test case.
The best idea is to do something like this and waiting for OOM:
| for _ = 1, 10000 do
|   misc.memprof.start("/tmp/tmp_memprofile.bin")
| end
But it's disgusting, so as I've discussed with Igor offline test case
will be ommited.

Side note: The test aims to hit LUA_ERRMEM and need to be run for a long
time. The exact reason we didn't face this failure is the omitted
<lua_close> in Tarantool.

src/lib_misc.c   | 4 ----
src/lj_memprof.c | 8 ++++++--
2 files changed, 6 insertions(+), 6 deletions(-)

<snipped>

-- 
2.28.0

-- 
Best regards,
IM