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Kernel: Enable timeout support for sys$futex(FUTEX_WAIT)

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Utilize the new Thread::wait_on timeout parameter to implement
timeout support for FUTEX_WAIT.

As we compute the relative time from the user specified absolute
time, we try to delay that computation as long as possible before
we call into Thread::wait_on(..). To enable this a small bit of
refactoring was done pull futex_queue fetching out and timeout fetch
and calculation separation.
This commit is contained in:
Brian Gianforcaro 2020-04-26 02:40:24 -07:00 • committed by Andreas Kling
parent faf15e3721
commit 25a620a573
1 changed files with 34 additions and 9 deletions
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43
Kernel/Process.cpp
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@ -2327,6 +2327,19 @@ timeval kgettimeofday()
return const_cast<const timeval&>(((KernelInfoPage*)s_info_page_address_for_kernel.as_ptr())->now);
}
void compute_relative_timeout_from_absolute(const timeval& absolute_time, timeval& relative_time)
{
// Convert absolute time to relative time of day.
timeval_sub(absolute_time, kgettimeofday(), relative_time);
}
void compute_relative_timeout_from_absolute(const timespec& absolute_time, timeval& relative_time)
{
timeval tv_absolute_time;
timespec_to_timeval(absolute_time, tv_absolute_time);
compute_relative_timeout_from_absolute(tv_absolute_time, relative_time);
}
void kgettimeofday(timeval& tv)
{
tv = kgettimeofday();
@ -4660,21 +4673,33 @@ int Process::sys$futex(const Syscall::SC_futex_params* user_params)
if (user_timeout && !validate_read_typed(user_timeout))
return -EFAULT;
timespec timeout { 0, 0 };
if (user_timeout)
copy_from_user(&timeout, user_timeout);
i32 user_value;
switch (futex_op) {
case FUTEX_WAIT:
case FUTEX_WAIT: {
i32 user_value;
copy_from_user(&user_value, userspace_address);
if (user_value != value)
return -EAGAIN;
timespec ts_abstimeout { 0, 0 };
if (user_timeout && !validate_read_and_copy_typed(&ts_abstimeout, user_timeout))
return -EFAULT;
WaitQueue& wait_queue = futex_queue(userspace_address);
timeval* optional_timeout = nullptr;
timeval relative_timeout { 0, 0 };
if (user_timeout) {
compute_relative_timeout_from_absolute(ts_abstimeout, relative_timeout);
optional_timeout = &relative_timeout;
}
// FIXME: This is supposed to be interruptible by a signal, but right now WaitQueue cannot be interrupted.
// FIXME: Support timeout!
Thread::current->wait_on(futex_queue(userspace_address));
Thread::BlockResult result = Thread::current->wait_on(wait_queue, optional_timeout);
if (result == Thread::BlockResult::InterruptedByTimeout) {
return -ETIMEDOUT;
}
break;
}
case FUTEX_WAKE:
if (value == 0)
return 0;