diff options
author | Julian Andres Klode <jak@debian.org> | 2017-01-29 13:05:18 +0100 |
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committer | Julian Andres Klode <julian.klode@canonical.com> | 2018-08-07 15:07:52 +0200 |
commit | c2c8b4787b0882234ba2772ec7513afbf97b563a (patch) | |
tree | f6c0634c45d174c00192356c49a3fd7fe583e396 /apt-pkg/tagfile-order.c | |
parent | 91671efc7f63b3e2ff2a573d86ac3225e9b5f9cd (diff) |
Add support for dpkg frontend lock
The dpkg frontend lock is a lock dpkg tries to acquire
except if the frontend already acquires it.
This fixes a race condition in the install command where the
dpkg lock is not held for a short period of time between
different dpkg invocations.
For this reason we also define an environment variable
DPKG_FRONTEND_LOCKED for dpkg invocations so dpkg knows
not to try to acquire the frontend lock because it's held
by a parent process.
We can set DPKG_FRONTEND_LOCKED only if the frontend lock
really is held; that is, if our lock count is greater than 0
- otherwise an apt client not using the LockInner family of
functions would run dpkg without the frontend lock set, but
with DPKG_FRONTEND_LOCKED set. Such a process has a weaker
guarantee: Because dpkg would not lock the frontend lock
either, the process is prone to the existing races, and,
more importantly, so is a new style process.
Closes: #869546
[fixups: fix error messages, add public IsLocked() method, and
make {Un,}LockInner return an error on !debSystem]
Diffstat (limited to 'apt-pkg/tagfile-order.c')
0 files changed, 0 insertions, 0 deletions