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From: Jeff King <peff@peff.net>
To: Matheus Tavares Bernardino <matheus.bernardino@usp.br>
Cc: "Jonathan Tan" <jonathantanmy@google.com>,
	git <git@vger.kernel.org>,
	"Christian Couder" <christian.couder@gmail.com>,
	"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: Thu, 14 Nov 2019 01:01:34 -0500	[thread overview]
Message-ID: <20191114060134.GB10643@sigill.intra.peff.net> (raw)
In-Reply-To: <CAHd-oW4PtO2CKpd3HFgrJWmQf3MN+MHt5c7V6OGx33LgU-CrOQ@mail.gmail.com>

On Thu, Nov 14, 2019 at 02:57:42AM -0300, Matheus Tavares Bernardino wrote:

> About the other parallel inflation calls on loose objects at
> unpack_loose_short_header(), unpack_loose_header_to_strbuf() and
> unpack_loose_rest(): could they suffer from a similar race problem?
> FWIU, the inflation input used in these cases comes from
> map_loose_object(), and it's not referenced outside this scope. So I
> think there's no risk of one thread munmapping the object file while
> other is inflating it. Is that right?

Right, I think loose objects would be fine, because the mmap'd content
is local to that stack variable.

> > A pthread_rwlock would work, but it would be the first use in Git. I
> > think we'd need to find an equivalent for compat/win32/pthread.h.
> 
> These[1][2] seems to be the equivalent options on Windows. I'll have
> to read these docs more carefully, but [2] seems to be more
> interesting in terms of speed. Also, the extra features of [1] are not
> really needed for our use case here.
> 
> [1]: https://docs.microsoft.com/en-us/windows-hardware/drivers/kernel/reader-writer-spin-locks
> [2]: https://docs.microsoft.com/en-us/windows/win32/sync/slim-reader-writer--srw--locks

Yeah, looks like it, but I don't have any expertise there (nor a Windows
system to test on).

-Peff

  reply	other threads:[~2019-11-14  6:01 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 [this message]
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
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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