Lower priorities of background tabs on linux.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/345009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@30470 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 63 insertions, 0 deletions

diff --git a/base/process_linux.cc b/base/process_linux.cc
new file mode 100644
index 0000000..30bc1f7
--- /dev/null
+++ b/base/process_linux.cc
@@ -0,0 +1,63 @@
+// Copyright (c) 2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/process.h"
+
+#include <errno.h>
+#include <sys/resource.h>
+
+#include "base/logging.h"
+
+namespace base {
+
+bool Process::IsProcessBackgrounded() const {
+  DCHECK(process_);
+  return saved_priority_ == kUnsetProcessPriority;
+}
+
+bool Process::SetProcessBackgrounded(bool background) {
+  DCHECK(process_);
+
+  if (background) {
+    // We won't be able to raise the priority if we don't have the right rlimit.
+    // The limit may be adjusted in /etc/security/limits.conf for PAM systems.
+    struct rlimit rlim;
+    if (getrlimit(RLIMIT_NICE, &rlim) != 0) {
+      // Call to getrlimit failed, don't background.
+      return false;
+    }
+    errno = 0;
+    int current_priority = GetPriority();
+    if (errno) {
+      // Couldn't get priority.
+      return false;
+    }
+    // {set,get}priority values are in the range -20 to 19, where -1 is higher
+    // priority than 0. But rlimit's are in the range from 0 to 39 where
+    // 1 is higher than 0.
+    if ((20 - current_priority) > static_cast<int>(rlim.rlim_cur)) {
+      // User is not allowed to raise the priority back to where it is now.
+      return false;
+    }
+    int result = setpriority(PRIO_PROCESS, process_, current_priority + 1);
+    if (result == -1) {
+      // Failed to lower priority.
+      return false;
+    }
+    saved_priority_ = current_priority;
+    return true;
+  } else {
+    if (saved_priority_ == kUnsetProcessPriority) {
+      // Can't restore if we were never backgrounded.
+      return false;
+    }
+    int result = setpriority(PRIO_PROCESS, process_, saved_priority_);
+    // If we can't restore something has gone terribly wrong.
+    DPCHECK(result == 0);
+    saved_priority_ = kUnsetProcessPriority;
+    return true;
+  }
+}
+
+}  // namespace base