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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/debsystem.h
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/debsystem.h')
-rw-r--r--apt-pkg/deb/debsystem.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/apt-pkg/deb/debsystem.h b/apt-pkg/deb/debsystem.h
index 9fdecb42f..9de3c8b4e 100644
--- a/apt-pkg/deb/debsystem.h
+++ b/apt-pkg/deb/debsystem.h
@@ -51,6 +51,10 @@ class debSystem : public pkgSystem
APT_HIDDEN static pid_t ExecDpkg(std::vector<std::string> const &sArgs, int * const inputFd, int * const outputFd, bool const DiscardOutput);
APT_HIDDEN static bool SupportsMultiArch();
APT_HIDDEN static std::vector<std::string> SupportedArchitectures();
+
+ APT_HIDDEN bool LockInner();
+ APT_HIDDEN bool UnLockInner(bool NoErrors=false);
+ APT_HIDDEN bool IsLocked();
};
extern debSystem debSys;