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/*
* Copyright (C) 2021 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "IPCSemaphore.h"
#include "Decoder.h"
#include "Encoder.h"
#include "WebCoreArgumentCoders.h"
#include <wtf/UniStdExtras.h>
#if OS(LINUX)
#include <poll.h>
#include <sys/eventfd.h>
#endif
namespace IPC {
Semaphore::Semaphore()
{
#if OS(LINUX)
m_fd = { eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK | EFD_SEMAPHORE), UnixFileDescriptor::Adopt };
#endif
}
Semaphore::Semaphore(UnixFileDescriptor&& fd)
: m_fd(WTFMove(fd))
{ }
Semaphore::Semaphore(Semaphore&&) = default;
Semaphore& Semaphore::operator=(Semaphore&&) = default;
Semaphore::~Semaphore()
{
destroy();
}
void Semaphore::signal()
{
#if OS(LINUX)
ASSERT_WITH_MESSAGE(m_fd.value() >= 0, "Signalling on an invalid semaphore object");
// Matching waitImpl() and EFD_SEMAPHORE semantics, increment the semaphore value by 1.
uint64_t value = 1;
while (true) {
int ret = write(m_fd.value(), &value, sizeof(uint64_t));
if (LIKELY(ret != -1 || errno != EINTR))
break;
}
#endif
}
#if OS(LINUX)
static bool waitImpl(int fd, int timeout)
{
struct pollfd pollfdValue { .fd = fd, .events = POLLIN, .revents = 0 };
int ret = 0;
// Iterate on polling while interrupts are thrown, otherwise bail out of the loop immediately.
while (true) {
ret = poll(&pollfdValue, 1, timeout);
if (LIKELY(ret != -1 || errno != EINTR))
break;
}
// Fail if the return value doesn't indicate the single file descriptor with only input events available.
if (ret != 1 || !!(pollfdValue.revents ^ POLLIN))
return false;
// There should be data for reading -- due to EFD_SEMAPHORE, it should be 1 packed into an 8-byte value.
uint64_t value = 0;
ret = read(fd, &value, sizeof(uint64_t));
if (ret != sizeof(uint64_t) || value != 1)
return false;
return true;
}
#endif
bool Semaphore::wait()
{
#if OS(LINUX)
ASSERT_WITH_MESSAGE(m_fd.value() >= 0, "Waiting on an invalid semaphore object");
return waitImpl(m_fd.value(), -1);
#else
return false;
#endif
}
bool Semaphore::waitFor(Timeout timeout)
{
#if OS(LINUX)
ASSERT_WITH_MESSAGE(m_fd.value() >= 0, "Waiting on an invalid semaphore object");
int timeoutValue = -1;
if (!timeout.isInfinity())
timeoutValue = int(timeout.secondsUntilDeadline().milliseconds());
return waitImpl(m_fd.value(), timeoutValue);
#else
return false;
#endif
}
void Semaphore::encode(Encoder& encoder) const
{
encoder << m_fd.duplicate();
}
std::optional<Semaphore> Semaphore::decode(Decoder& decoder)
{
std::optional<UnixFileDescriptor> fd;
decoder >> fd;
if (!fd)
return std::nullopt;
return std::optional<Semaphore> { std::in_place, WTFMove(*fd) };
}
void Semaphore::destroy()
{
m_fd = { };
}
} // namespace IPC
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