884985 - Fix race condition in deleting the TMPDIR during boot

Status: RESOLVED FIXED

(Firefox OS Graveyard :: General, defect)

Description

[Inder]

Attachment: Fix race condition in TMPDIR creation

TMPDIR /data/local/tmp directory is getting removed after being created during boot! It turns out that this command in boot event:  https://github.com/mozilla-b2g/gonk-misc/blob/master/init.b2g.rc#L20 is occurring after the tmp directory is created here: https://github.com/mozilla-b2g/gonk-misc/blob/master/b2g.sh#L4 so, we end up having no tmp dir after a clean boot. We need to serialize the deletion and creation.

Comment 1

[Michael Wu [:mwu]]

Comment on attachment 764952 [details] [diff] [review]
Fix race condition in TMPDIR creation

Review of attachment 764952 [details] [diff] [review]:
-----------------------------------------------------------------

::: init.b2g.rc
@@ -16,5 @@
>      user root
>      group radio
>  
>  on boot
> -    exec /system/bin/rm -r /data/local/tmp

Does doing /data/local/tmp/* instead work? IIRC, we wanted to clear tmp only once on boot rather than every time b2g.sh is called.

Comment 2

[Michael Vines [:m1] [:evilmachines]]

Looks like the globbing wouldn't work as exec is just a wrapper around fork+execl, but this might work:
 
 on boot
    exec /system/bin/sh -c '/system/bin/rm -r /data/local/tmp/*'

Do you recall the use case for why clearing tmp on every b2g.sh invocation is a problem?Developer nuisance?

Comment 3

[Michael Wu [:mwu]]

I think it was just done out of paranoia.

Another option might be to move all of the /data/local/tmp deletion/regeneration/cleanup to init.b2g.rc, and then make sure that stuff executes before we switch to booting services in the main class.

Comment 4

[Inder]

Based to m1's suggestion I tried this:
 on boot
    exec /system/bin/sh -c '/system/bin/rm -r /data/local/tmp'

And, this seems to work fine. I don't see any indexedDB errors and tmp dir gets created properly.

I didn't want to do globbing as it may mask the issue. In case of race condition it may wipe temp files when other programs were in middle of creating/using it. If we delete the directory then at least there are more chances of the error getting reported.

If we are okay with doing this then I will update the PR.

Comment 5

[Inder]

Attachment: updated patch

Discussed with m1 offline and realized why he added the shell there!
Based on mwu's suggestion in comment 3 updating the patch to move the creation of tmp also in init.b2g.rc.
I have also updated the PR: https://github.com/mozilla-b2g/gonk-misc/pull/100

Comment 6

[Michael Vines [:m1] [:evilmachines]]

https://github.com/mozilla-b2g/gonk-misc/commit/f0c701dad1c7352d567f4ddcf86c66ae2d5c8fda