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base / allocator / partition_allocator / src / partition_alloc / partition_lock.h [blame]
// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef PARTITION_ALLOC_PARTITION_LOCK_H_
#define PARTITION_ALLOC_PARTITION_LOCK_H_
#include <atomic>
#include <type_traits>
#include "partition_alloc/build_config.h"
#include "partition_alloc/buildflags.h"
#include "partition_alloc/partition_alloc_base/compiler_specific.h"
#include "partition_alloc/partition_alloc_base/immediate_crash.h"
#include "partition_alloc/partition_alloc_base/thread_annotations.h"
#include "partition_alloc/partition_alloc_base/threading/platform_thread.h"
#include "partition_alloc/partition_alloc_check.h"
#include "partition_alloc/spinning_mutex.h"
#include "partition_alloc/thread_isolation/thread_isolation.h"
namespace partition_alloc::internal {
class PA_LOCKABLE Lock {
public:
inline constexpr Lock();
void Acquire() PA_EXCLUSIVE_LOCK_FUNCTION() {
#if PA_BUILDFLAG(DCHECKS_ARE_ON) || \
PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
#if PA_BUILDFLAG(ENABLE_THREAD_ISOLATION)
LiftThreadIsolationScope lift_thread_isolation_restrictions;
#endif
// When PartitionAlloc is malloc(), it can easily become reentrant. For
// instance, a DCHECK() triggers in external code (such as
// base::Lock). DCHECK() error message formatting allocates, which triggers
// PartitionAlloc, and then we get reentrancy, and in this case infinite
// recursion.
//
// To avoid that, crash quickly when the code becomes reentrant.
base::PlatformThreadRef current_thread = base::PlatformThread::CurrentRef();
if (!lock_.Try()) {
// The lock wasn't free when we tried to acquire it. This can be because
// another thread or *this* thread was holding it.
//
// If it's this thread holding it, then it cannot have become free in the
// meantime, and the current value of |owning_thread_ref_| is valid, as it
// was set by this thread. Assuming that writes to |owning_thread_ref_|
// are atomic, then if it's us, we are trying to recursively acquire a
// non-recursive lock.
//
// Note that we don't rely on a DCHECK() in base::Lock(), as it would
// itself allocate. Meaning that without this code, a reentrancy issue
// hangs on Linux.
if (owning_thread_ref_.load(std::memory_order_acquire) == current_thread)
[[unlikely]] {
// Trying to acquire lock while it's held by this thread: reentrancy
// issue.
ReentrancyIssueDetected();
}
lock_.Acquire();
}
owning_thread_ref_.store(current_thread, std::memory_order_release);
#else
lock_.Acquire();
#endif // PA_BUILDFLAG(DCHECKS_ARE_ON) ||
// PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
}
void Release() PA_UNLOCK_FUNCTION() {
#if PA_BUILDFLAG(DCHECKS_ARE_ON) || \
PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
#if PA_BUILDFLAG(ENABLE_THREAD_ISOLATION)
LiftThreadIsolationScope lift_thread_isolation_restrictions;
#endif
owning_thread_ref_.store(base::PlatformThreadRef(),
std::memory_order_release);
#endif // PA_BUILDFLAG(DCHECKS_ARE_ON) ||
// PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
lock_.Release();
}
void AssertAcquired() const PA_ASSERT_EXCLUSIVE_LOCK() {
lock_.AssertAcquired();
#if PA_BUILDFLAG(DCHECKS_ARE_ON) || \
PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
#if PA_BUILDFLAG(ENABLE_THREAD_ISOLATION)
LiftThreadIsolationScope lift_thread_isolation_restrictions;
#endif
PA_DCHECK(owning_thread_ref_.load(std ::memory_order_acquire) ==
base::PlatformThread::CurrentRef());
#endif // PA_BUILDFLAG(DCHECKS_ARE_ON) ||
// PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
}
void Reinit() PA_UNLOCK_FUNCTION() {
lock_.AssertAcquired();
#if PA_BUILDFLAG(DCHECKS_ARE_ON) || \
PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
owning_thread_ref_.store(base::PlatformThreadRef(),
std::memory_order_release);
#endif // PA_BUILDFLAG(DCHECKS_ARE_ON) ||
// PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
lock_.Reinit();
}
private:
[[noreturn]] PA_NOINLINE PA_NOT_TAIL_CALLED void ReentrancyIssueDetected() {
PA_NO_CODE_FOLDING();
PA_IMMEDIATE_CRASH();
}
SpinningMutex lock_;
#if PA_BUILDFLAG(DCHECKS_ARE_ON) || \
PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
// Should in theory be protected by |lock_|, but we need to read it to detect
// recursive lock acquisition (and thus, the allocator becoming reentrant).
std::atomic<base::PlatformThreadRef> owning_thread_ref_ =
base::PlatformThreadRef();
#endif // PA_BUILDFLAG(DCHECKS_ARE_ON) ||
// PA_BUILDFLAG(ENABLE_PARTITION_LOCK_REENTRANCY_CHECK)
};
class PA_SCOPED_LOCKABLE ScopedGuard {
public:
explicit ScopedGuard(Lock& lock) PA_EXCLUSIVE_LOCK_FUNCTION(lock)
: lock_(lock) {
lock_.Acquire();
}
~ScopedGuard() PA_UNLOCK_FUNCTION() { lock_.Release(); }
private:
Lock& lock_;
};
class PA_SCOPED_LOCKABLE ScopedUnlockGuard {
public:
explicit ScopedUnlockGuard(Lock& lock) PA_UNLOCK_FUNCTION(lock)
: lock_(lock) {
lock_.Release();
}
~ScopedUnlockGuard() PA_EXCLUSIVE_LOCK_FUNCTION() { lock_.Acquire(); }
private:
Lock& lock_;
};
constexpr Lock::Lock() = default;
// We want PartitionRoot to not have a global destructor, so this should not
// have one.
static_assert(std::is_trivially_destructible_v<Lock>, "");
} // namespace partition_alloc::internal
namespace base {
namespace internal {
using PartitionLock = ::partition_alloc::internal::Lock;
using PartitionAutoLock = ::partition_alloc::internal::ScopedGuard;
} // namespace internal
} // namespace base
#endif // PARTITION_ALLOC_PARTITION_LOCK_H_