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authorJulian Andres Klode <jak@debian.org>2017-01-29 13:05:18 +0100
committerJulian Andres Klode <julian.klode@canonical.com>2018-09-28 13:11:08 +0200
commit6c0c94ed32b8e679b14b0f89b51c1c336dc0ab9c (patch)
tree71e50645d0876d37cf9978e095e4ea9578cda690 /apt-pkg/deb/dpkgpm.cc
parent409ceec9ed30cbebd8ece1ef7ce667ab5a32f9df (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] (cherry picked from commit c2c8b4787b0882234ba2772ec7513afbf97b563a) LP: #1781169
Diffstat (limited to 'apt-pkg/deb/dpkgpm.cc')
-rw-r--r--apt-pkg/deb/dpkgpm.cc4
1 files changed, 4 insertions, 0 deletions
diff --git a/apt-pkg/deb/dpkgpm.cc b/apt-pkg/deb/dpkgpm.cc
index c6900ec77..790019b98 100644
--- a/apt-pkg/deb/dpkgpm.cc
+++ b/apt-pkg/deb/dpkgpm.cc
@@ -2010,6 +2010,10 @@ bool pkgDPkgPM::Go(APT::Progress::PackageManager *progress)
else
setenv("DPKG_COLORS", "never", 0);
+ if (dynamic_cast<debSystem*>(_system) != nullptr
+ && dynamic_cast<debSystem*>(_system)->IsLocked() == true) {
+ setenv("DPKG_FRONTEND_LOCKED", "true", 1);
+ }
execvp(Args[0], (char**) &Args[0]);
cerr << "Could not exec dpkg!" << endl;
_exit(100);