From 93e1565796b61eb44bec39f50e09a34cbe090178 Mon Sep 17 00:00:00 2001
From: Julian Andres Klode <julian.klode@canonical.com>
Date: Wed, 26 Feb 2020 20:31:03 +0100
Subject: apt(8): Wait for frontend and cache lock

This is a rework of !6 with additional stuff for the frontend
lock, so we can lock the frontend lock and then keep looping
over dpkg lock.
---
 apt-pkg/deb/debsystem.cc | 50 +++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 45 insertions(+), 5 deletions(-)

(limited to 'apt-pkg/deb/debsystem.cc')

diff --git a/apt-pkg/deb/debsystem.cc b/apt-pkg/deb/debsystem.cc
index 225761e9d..da7ae2e42 100644
--- a/apt-pkg/deb/debsystem.cc
+++ b/apt-pkg/deb/debsystem.cc
@@ -19,8 +19,10 @@
 #include <apt-pkg/error.h>
 #include <apt-pkg/fileutl.h>
 #include <apt-pkg/pkgcache.h>
+#include <apt-pkg/progress.h>
 
 #include <algorithm>
+#include <sstream>
 
 #include <string>
 #include <vector>
@@ -75,7 +77,42 @@ debSystem::~debSystem()
 // ---------------------------------------------------------------------
 /* This mirrors the operations dpkg does when it starts up. Note the
    checking of the updates directory. */
-bool debSystem::Lock()
+static int GetLockMaybeWait(std::string const &file, OpProgress *Progress, int &timeoutSec)
+{
+   int fd = -1;
+   if (timeoutSec == 0 || Progress == nullptr)
+      return GetLock(file);
+
+   if (_config->FindB("Debug::Locking", false))
+      std::cerr << "Lock: " << file << " wait " << timeoutSec << std::endl;
+
+   for (int i = 0; timeoutSec < 0 || i < timeoutSec; i++)
+   {
+      _error->PushToStack();
+      fd = GetLock(file);
+      if (fd != -1 || errno == EPERM)
+      {
+	 if (timeoutSec > 0)
+	    timeoutSec -= i;
+	 _error->MergeWithStack();
+	 return fd;
+      }
+      std::string poppedError;
+      std::string completeError;
+      _error->PopMessage(poppedError);
+      _error->RevertToStack();
+
+      strprintf(completeError, _("Waiting for cache lock (%s)"), poppedError.c_str());
+      sleep(1);
+      Progress->OverallProgress(i, timeoutSec, 0, completeError);
+   }
+
+   if (timeoutSec > 0)
+      timeoutSec = 1;
+   return fd;
+}
+
+bool debSystem::Lock(OpProgress *const Progress)
 {
    // Disable file locking
    if (_config->FindB("Debug::NoLocking",false) == true || d->LockCount > 0)
@@ -84,10 +121,12 @@ bool debSystem::Lock()
       return true;
    }
 
+   // This will count downwards.
+   int lockTimeOutSec = _config->FindI("DPkg::Lock::Timeout", 0);
    // Create the lockfile
    string AdminDir = flNotFile(_config->FindFile("Dir::State::status"));
    string FrontendLockFile = AdminDir + "lock-frontend";
-   d->FrontendLockFD = GetLock(FrontendLockFile);
+   d->FrontendLockFD = GetLockMaybeWait(FrontendLockFile, Progress, lockTimeOutSec);
    if (d->FrontendLockFD == -1)
    {
       if (errno == EACCES || errno == EAGAIN)
@@ -97,7 +136,7 @@ bool debSystem::Lock()
 	 return _error->Error(_("Unable to acquire the dpkg frontend lock (%s), "
 	                        "are you root?"),FrontendLockFile.c_str());
    }
-   if (LockInner() == false)
+   if (LockInner(Progress, lockTimeOutSec) == false)
    {
       close(d->FrontendLockFD);
       return false;
@@ -126,9 +165,10 @@ bool debSystem::Lock()
    return true;
 }
 
-bool debSystem::LockInner() {
+bool debSystem::LockInner(OpProgress *const Progress, int timeOutSec)
+{
    string AdminDir = flNotFile(_config->FindFile("Dir::State::status"));
-   d->LockFD = GetLock(AdminDir + "lock");
+   d->LockFD = GetLockMaybeWait(AdminDir + "lock", Progress, timeOutSec);
    if (d->LockFD == -1)
    {
       if (errno == EACCES || errno == EAGAIN)
-- 
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