arc: Protect CloudDPC process from been killed by memory killer.

This adds explicit rule to protect CloudDPC

Test: unit_test
Bug: b:73064229
Change-Id: If56eec0800d3a7be4c2a1775e6ceedec0583833f
Reviewed-on: https://chromium-review.googlesource.com/996568Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Commit-Queue: Yury Khmel <khmel@google.com>
Cr-Commit-Position: refs/heads/master@{#548572}

chrome/browser/chromeos/arc/process/arc_process.cc

@@ -10,6 +10,9 @@
 
 namespace arc {
 
+constexpr char kCloudDpcrocessName[] =
+    "com.google.android.apps.work.clouddpc.arc";
+
 ArcProcess::ArcProcess(base::ProcessId nspid,
                        base::ProcessId pid,
                        const std::string& process_name,
@@ -37,14 +40,20 @@ ArcProcess::ArcProcess(ArcProcess&& other) = default;
 ArcProcess& ArcProcess::operator=(ArcProcess&& other) = default;
 
 bool ArcProcess::IsImportant() const {
-  return process_state() <= mojom::ProcessState::IMPORTANT_FOREGROUND;
+  return process_state() <= mojom::ProcessState::IMPORTANT_FOREGROUND ||
+         IsArcProtected();
 }
 
 bool ArcProcess::IsKernelKillable() const {
-  // Protect PERSISTENT, PERSISTENT_UI, and our HOME processes since they should
-  // never be killed even by the kernel. Returning false for them allows their
-  // OOM adjustment scores to remain negative.
-  return process_state() > arc::mojom::ProcessState::PERSISTENT_UI;
+  // Protect PERSISTENT, PERSISTENT_UI, our HOME and custom set of ARC processes
+  // since they should never be killed even by the kernel. Returning false for
+  // them allows their OOM adjustment scores to remain negative.
+  return process_state() > arc::mojom::ProcessState::PERSISTENT_UI &&
+         !IsArcProtected();
+}
+
+bool ArcProcess::IsArcProtected() const {
+  return process_name() == kCloudDpcrocessName;
 }
 
 std::ostream& operator<<(std::ostream& out, const ArcProcess& arc_process) {

chrome/browser/chromeos/arc/process/arc_process.h

@@ -53,6 +53,9 @@ class ArcProcess {
   bool IsKernelKillable() const;
 
  private:
+  // Returns true if this is ARC protected process which we don't allow to kill.
+  bool IsArcProtected() const;
+
   base::ProcessId nspid_;
   base::ProcessId pid_;
   std::string process_name_;

chrome/browser/chromeos/arc/process/arc_process_unittest.cc

@@ -122,12 +122,17 @@ TEST(ArcProcess, TestIsImportant) {
   EXPECT_FALSE(ArcProcess(0, 0, "process", mojom::ProcessState::CACHED_EMPTY,
                           kIsNotFocused, 0)
                    .IsImportant());
+
+  // Custom ARC protected processes.
+  EXPECT_TRUE(ArcProcess(0, 0, "com.google.android.apps.work.clouddpc.arc",
+                         mojom::ProcessState::SERVICE, kIsNotFocused, 0)
+                  .IsImportant());
 }
 
 TEST(ArcProcess, TestIsKernelKillable) {
   constexpr bool kIsNotFocused = false;
 
-  // Only PERSISITENT* processes are protected from the kernel OOM killer.
+  // PERSISITENT* processes are protected from the kernel OOM killer.
   EXPECT_FALSE(ArcProcess(0, 0, "process", mojom::ProcessState::PERSISTENT,
                           kIsNotFocused, 0)
                    .IsKernelKillable());
@@ -189,6 +194,11 @@ TEST(ArcProcess, TestIsKernelKillable) {
   EXPECT_TRUE(ArcProcess(0, 0, "process", mojom::ProcessState::CACHED_EMPTY,
                          kIsNotFocused, 0)
                   .IsKernelKillable());
+
+  // Set of custom processes that are protected from the kernel OOM killer.
+  EXPECT_FALSE(ArcProcess(0, 0, "com.google.android.apps.work.clouddpc.arc",
+                          mojom::ProcessState::SERVICE, kIsNotFocused, 0)
+                   .IsKernelKillable());
 }
 
 // Tests operator<<() does not crash and returns non-empty result, at least.