1 files changed, 17 insertions, 4 deletions
diff --git a/test/syscalls/linux/itimer.cc b/test/syscalls/linux/itimer.cc
index dd981a278..e397d5f57 100644
--- a/test/syscalls/linux/itimer.cc
+++ b/test/syscalls/linux/itimer.cc
@@ -267,8 +267,19 @@ int TestSIGPROFFairness(absl::Duration sleep) {
 // Random save/restore is disabled as it introduces additional latency and
 // unpredictable distribution patterns.
 TEST(ItimerTest, DeliversSIGPROFToThreadsRoughlyFairlyActive_NoRandomSave) {
-  // TODO(b/143247272): CPU time accounting is inaccurate for the KVM platform.
-  SKIP_IF(GvisorPlatform() == Platform::kKVM);
+  // On the KVM and ptrace platforms, switches between sentry and application
+  // context are sometimes extremely slow, causing the itimer to send SIGPROF to
+  // a thread that either already has one pending or has had SIGPROF delivered,
+  // but hasn't handled it yet (and thus therefore still has SIGPROF masked). In
+  // either case, since itimer signals are group-directed, signal sending falls
+  // back to notifying the thread group leader. ItimerSignalTest() fails if "too
+  // many" signals are delivered to the thread group leader, so these tests are
+  // flaky on these platforms.
+  //
+  // TODO(b/143247272): Clarify why context switches are so slow on KVM.
+  const auto gvisor_platform = GvisorPlatform();
+  SKIP_IF(gvisor_platform == Platform::kKVM ||
+          gvisor_platform == Platform::kPtrace);
 
   pid_t child;
   int execve_errno;
@@ -291,8 +302,10 @@ TEST(ItimerTest, DeliversSIGPROFToThreadsRoughlyFairlyActive_NoRandomSave) {
 // Random save/restore is disabled as it introduces additional latency and
 // unpredictable distribution patterns.
 TEST(ItimerTest, DeliversSIGPROFToThreadsRoughlyFairlyIdle_NoRandomSave) {
-  // TODO(b/143247272): CPU time accounting is inaccurate for the KVM platform.
-  SKIP_IF(GvisorPlatform() == Platform::kKVM);
+  // See comment in DeliversSIGPROFToThreadsRoughlyFairlyActive.
+  const auto gvisor_platform = GvisorPlatform();
+  SKIP_IF(gvisor_platform == Platform::kKVM ||
+          gvisor_platform == Platform::kPtrace);
 
   pid_t child;
   int execve_errno;