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Second try at flaky futex test. 

The flake had the call to futex_unlock_pi() returning EINVAL with the
FUTEX_OWNER_DIED set. In this case, userspace has to clean up stale
state. So instead of calling FUTEX_UNLOCK_PI outright, we'll use the
advised atomic compare_exchange as advised in the man page.

PiperOrigin-RevId: 265163920
This commit is contained in:
Zach Koopmans 2019-08-23 16:53:00 -07:00 committed by gVisor bot
parent e75a12e89d
commit a5d0115943
1 changed files with 14 additions and 2 deletions
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16
test/syscalls/linux/futex.cc
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@ -125,6 +125,10 @@ int futex_lock_pi(bool priv, std::atomic<int>* uaddr) {
if (priv) {
op |= FUTEX_PRIVATE_FLAG;
}
int zero = 0;
if (uaddr->compare_exchange_strong(zero, gettid())) {
return 0;
}
return RetryEINTR(syscall)(SYS_futex, uaddr, op, nullptr, nullptr);
}
@ -133,6 +137,10 @@ int futex_trylock_pi(bool priv, std::atomic<int>* uaddr) {
if (priv) {
op |= FUTEX_PRIVATE_FLAG;
}
int zero = 0;
if (uaddr->compare_exchange_strong(zero, gettid())) {
return 0;
}
return RetryEINTR(syscall)(SYS_futex, uaddr, op, nullptr, nullptr);
}
@ -141,6 +149,10 @@ int futex_unlock_pi(bool priv, std::atomic<int>* uaddr) {
if (priv) {
op |= FUTEX_PRIVATE_FLAG;
}
int tid = gettid();
if (uaddr->compare_exchange_strong(tid, 0)) {
return 0;
}
return RetryEINTR(syscall)(SYS_futex, uaddr, op, nullptr, nullptr);
}
@ -692,8 +704,8 @@ TEST_P(PrivateAndSharedFutexTest, PITryLockConcurrency_NoRandomSave) {
std::unique_ptr<ScopedThread> threads[10];
for (size_t i = 0; i < ABSL_ARRAYSIZE(threads); ++i) {
threads[i] = absl::make_unique<ScopedThread>([is_priv, &a] {
for (size_t j = 0; j < 100;) {
if (futex_trylock_pi(is_priv, &a) >= 0) {
for (size_t j = 0; j < 10;) {
if (futex_trylock_pi(is_priv, &a) == 0) {
++j;
EXPECT_EQ(a.load() & FUTEX_TID_MASK, gettid());
SleepSafe(absl::Milliseconds(5));