From: Jeff King <peff@peff.net>
To: Michael Haggerty <mhagger@alum.mit.edu>
Cc: "Johannes Sixt" <j.sixt@viscovery.net>,
"Junio C Hamano" <gitster@pobox.com>,
git@vger.kernel.org, "Torsten Bögershausen" <tboegi@web.de>,
"Eric Sunshine" <sunshine@sunshineco.com>
Subject: Re: [PATCH v2 18/25] lockfile: avoid transitory invalid states
Date: Mon, 7 Apr 2014 15:38:34 -0400 [thread overview]
Message-ID: <20140407193834.GD19342@sigill.intra.peff.net> (raw)
In-Reply-To: <5342A451.5020905@alum.mit.edu>
On Mon, Apr 07, 2014 at 03:12:49PM +0200, Michael Haggerty wrote:
> > How far *do* you want to go? I'm certainly not opposed to field-test your
> > current changeset (plus and adjustment to use sig_atomic_t) -- overall it
> > is an improvement. And then we will see how it works.
>
> For now I think I'd just like to get the biggest problems fixed without
> making anything worse. Given that there might be a GSoC student working
> in this neighborhood, he/she might be able to take up the baton.
>
> I changed the patch series to use a new "volatile sig_atomic_t active"
> field rather than a bit in a "flags" field.
That seems like a good place to stop for now.
If any code touches the fields, it can unset the "active" flag (even
temporarily), and restore it when the structure is in a known state.
I'm not sure if we can ever reach full safety. If you have an event
loop, the sane thing to do is set an atomic flag in your signal handler
and then handle it on the next iteration of the loop. But all of our
signal handlers are jumped to from arbitrary code, and are just going to
die(). There's nothing to return to, so any useful work we do has to be
done from the handler.
-Peff
next prev parent reply other threads:[~2014-04-07 19:38 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-06 23:33 [PATCH v2 00/25] Lockfile correctness and refactoring Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 01/25] api-lockfile: expand the documentation Michael Haggerty
2014-04-07 18:46 ` Jeff King
2014-04-06 23:33 ` [PATCH v2 02/25] unable_to_lock_die(): rename function from unable_to_lock_index_die() Michael Haggerty
2014-04-07 18:47 ` Jeff King
2014-04-08 14:04 ` Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 03/25] rollback_lock_file(): do not clear filename redundantly Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 04/25] rollback_lock_file(): set fd to -1 Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 05/25] lockfile: unlock file if lockfile permissions cannot be adjusted Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 06/25] hold_lock_file_for_append(): release lock on errors Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 07/25] lock_file(): always add lock_file object to lock_file_list Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 08/25] struct lock_file: replace on_list field with flags field Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 09/25] lockfile.c: document the various states of lock_file objects Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 10/25] lockfile: define a constant LOCK_SUFFIX_LEN Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 11/25] delete_ref_loose(): don't muck around in the lock_file's filename Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 12/25] prepare_index(): declare return value to be (const char *) Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 13/25] write_packed_entry_fn(): convert cb_data into a (const int *) Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 14/25] lock_file(): exit early if lockfile cannot be opened Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 15/25] remove_lock_file(): call rollback_lock_file() Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 16/25] commit_lock_file(): inline temporary variable Michael Haggerty
2014-04-06 23:33 ` [PATCH v2 17/25] commit_lock_file(): make committing an unlocked lockfile a NOP Michael Haggerty
2014-04-07 19:31 ` Jeff King
2014-04-14 8:21 ` Michael Haggerty
2014-04-06 23:34 ` [PATCH v2 18/25] lockfile: avoid transitory invalid states Michael Haggerty
2014-04-07 6:16 ` Johannes Sixt
2014-04-07 11:13 ` Michael Haggerty
2014-04-07 12:12 ` Johannes Sixt
2014-04-07 13:12 ` Michael Haggerty
2014-04-07 19:38 ` Jeff King [this message]
2014-04-06 23:34 ` [PATCH v2 19/25] try_merge_strategy(): remove redundant lock_file allocation Michael Haggerty
2014-04-06 23:34 ` [PATCH v2 20/25] try_merge_strategy(): use a statically-allocated lock_file object Michael Haggerty
2014-04-06 23:34 ` [PATCH v2 21/25] commit_lock_file(): use a strbuf to manage temporary space Michael Haggerty
2014-04-06 23:34 ` [PATCH v2 22/25] Change lock_file::filename into a strbuf Michael Haggerty
2014-04-06 23:34 ` [PATCH v2 23/25] resolve_symlink(): use a strbuf for internal scratch space Michael Haggerty
2014-04-06 23:34 ` [PATCH v2 24/25] resolve_symlink(): take a strbuf parameter Michael Haggerty
2014-04-06 23:34 ` [PATCH v2 25/25] trim_last_path_elm(): replace last_path_elm() Michael Haggerty
2014-04-07 19:40 ` [PATCH v2 00/25] Lockfile correctness and refactoring Jeff King
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