From: Christian Couder <christian.couder@gmail.com>
To: Matheus Tavares Bernardino <matheus.bernardino@usp.br>
Cc: "Jeff King" <peff@peff.net>,
"Jonathan Tan" <jonathantanmy@google.com>,
git <git@vger.kernel.org>,
"Оля Тележная" <olyatelezhnaya@gmail.com>,
"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
"Junio C Hamano" <gitster@pobox.com>,
"Jonathan Nieder" <jrnieder@gmail.com>,
"Stefan Beller" <stefanbeller@gmail.com>
Subject: Re: [PATCH v2 05/11] object-store: allow threaded access to object reading
Date: Fri, 10 Jan 2020 20:07:07 +0100 [thread overview]
Message-ID: <CAP8UFD3QHNoePGsc9t0fVxTJpPy+KBCbPfXKGoNOx_2bCf1Hxg@mail.gmail.com> (raw)
In-Reply-To: <CAHd-oW7WhSs2PDSwhksu0Kh5pAJE3rw3nmc-8VJ9dkJitz_N8A@mail.gmail.com>
Hi Matheus,
On Thu, Jan 9, 2020 at 11:02 PM Matheus Tavares Bernardino
<matheus.bernardino@usp.br> wrote:
>
> On Thu, Dec 19, 2019 at 5:27 PM Matheus Tavares Bernardino
> <matheus.bernardino@usp.br> wrote:
> > However, re-inspecting the code, it seemed to me that we might already
> > have a thread-safe mechanism. The window disposal operations (at
> > close_pack_windows() and unuse_one_window()) are only performed if
> > window.inuse_cnt == 0. So as a thread which reads from the window will
> > also previously increment its inuse_cnt, wouldn't the reading
> > operation be already protected?
> >
> > Another concern would be close_pack_fd(), which can close packs even
> > with in-use windows. However, as the mmap docs[1] says: "closing the
> > file descriptor does not unmap the region".
> >
> > Finally, we also considered reprepare_packed_git() as a possible
> > conflicting operation. But the function called by it to handle
> > packfile opening, prepare_pack(), won't reopen already available
> > packs. Therefore, IIUC, it will leave the opened windows intact.
> >
> > So, aren't perhaps the window readings performed outside the
> > obj_read_mutex critical section already thread-safe?
>
> Any thoughts on this?
My advice, if you don't hear from anyone in the next few days, is to
update the commit message, the cover letter and the comments inside
the patches with the information you researched and to resubmit a new
version of the patch series.
Thanks,
Christian.
next prev parent reply other threads:[~2020-01-10 19:07 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-10 20:27 [GSoC][PATCH 0/4] grep: re-enable threads when cached, w/ parallel inflation Matheus Tavares
2019-08-10 20:27 ` [GSoC][PATCH 1/4] object-store: add lock to read_object_file_extended() Matheus Tavares
2019-08-10 20:27 ` [GSoC][PATCH 2/4] grep: allow locks to be enabled individually Matheus Tavares
2019-08-10 20:27 ` [GSoC][PATCH 3/4] grep: disable grep_read_mutex when possible Matheus Tavares
2019-08-10 20:27 ` [GSoC][PATCH 4/4] grep: re-enable threads in some non-worktree cases Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 00/11] grep: improve threading and fix race conditions Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 01/11] grep: fix race conditions on userdiff calls Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 02/11] grep: fix race conditions at grep_submodule() Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 03/11] grep: fix racy calls in grep_objects() Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 04/11] replace-object: make replace operations thread-safe Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 05/11] object-store: allow threaded access to object reading Matheus Tavares
2019-11-12 2:54 ` Jonathan Tan
2019-11-13 5:20 ` Jeff King
2019-11-14 5:57 ` Matheus Tavares Bernardino
2019-11-14 6:01 ` Jeff King
2019-11-14 18:15 ` Jonathan Tan
2019-11-15 4:12 ` Jeff King
2019-12-19 22:27 ` Matheus Tavares Bernardino
2020-01-09 22:02 ` Matheus Tavares Bernardino
2020-01-10 19:07 ` Christian Couder [this message]
2019-09-30 1:50 ` [PATCH v2 06/11] grep: replace grep_read_mutex by internal obj read lock Matheus Tavares
2019-10-01 19:23 ` [PATCH] squash! " Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 07/11] submodule-config: add skip_if_read option to repo_read_gitmodules() Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 08/11] grep: allow submodule functions to run in parallel Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 09/11] grep: protect packed_git [re-]initialization Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 10/11] grep: re-enable threads in non-worktree case Matheus Tavares
2019-09-30 1:50 ` [PATCH v2 11/11] grep: move driver pre-load out of critical section Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 00/12] grep: improve threading and fix race conditions Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 01/12] grep: fix race conditions on userdiff calls Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 02/12] grep: fix race conditions at grep_submodule() Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 03/12] grep: fix racy calls in grep_objects() Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 04/12] replace-object: make replace operations thread-safe Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 05/12] object-store: allow threaded access to object reading Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 06/12] grep: replace grep_read_mutex by internal obj read lock Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 07/12] submodule-config: add skip_if_read option to repo_read_gitmodules() Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 08/12] grep: allow submodule functions to run in parallel Matheus Tavares
2020-01-29 11:26 ` SZEDER Gábor
2020-01-29 18:49 ` Junio C Hamano
2020-01-29 18:57 ` Junio C Hamano
2020-01-29 20:42 ` Matheus Tavares Bernardino
2020-01-30 13:28 ` Philippe Blain
2020-01-16 2:39 ` [PATCH v3 09/12] grep: protect packed_git [re-]initialization Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 10/12] grep: re-enable threads in non-worktree case Matheus Tavares
2020-01-16 2:39 ` [PATCH v3 11/12] grep: move driver pre-load out of critical section Matheus Tavares
2020-01-16 2:40 ` [PATCH v3 12/12] grep: use no. of cores as the default no. of threads Matheus Tavares
2020-01-16 13:11 ` Victor Leschuk
2020-01-16 14:47 ` [PATCH] " Matheus Tavares
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