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Kernel: Some futex improvements

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This adds support for FUTEX_WAKE_OP, FUTEX_WAIT_BITSET, FUTEX_WAKE_BITSET,
FUTEX_REQUEUE, and FUTEX_CMP_REQUEUE, as well well as global and private
futex and absolute/relative timeouts against the appropriate clock. This
also changes the implementation so that kernel resources are only used when
a thread is blocked on a futex.

Global futexes are implemented as offsets in VMObjects, so that different
processes can share a futex against the same VMObject despite potentially
being mapped at different virtual addresses.
This commit is contained in:
Tom 2020-12-21 23:21:58 -07:00 • committed by Andreas Kling
parent 7581b64705
commit 1d621ab172
23 changed files with 928 additions and 63 deletions
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34
Userland/Libraries/LibC/serenity.cpp
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@ -60,10 +60,38 @@ int profiling_disable(pid_t pid)
__RETURN_WITH_ERRNO(rc, rc, -1);
}
int futex(int32_t* userspace_address, int futex_op, int32_t value, const struct timespec* timeout)
int futex(uint32_t* userspace_address, int futex_op, uint32_t value, const struct timespec* timeout, uint32_t* userspace_address2, uint32_t value3)
{
Syscall::SC_futex_params params { userspace_address, futex_op, value, timeout };
int rc = syscall(SC_futex, &params);
int rc;
switch (futex_op & FUTEX_CMD_MASK) {
//case FUTEX_CMP_REQUEUE:
// FUTEX_CMP_REQUEUE_PI:
case FUTEX_WAKE_OP: {
// These interpret timeout as a u32 value for val2
Syscall::SC_futex_params params {
.userspace_address = userspace_address,
.futex_op = futex_op,
.val = value,
.val2 = (uint32_t)timeout,
.userspace_address2 = userspace_address2,
.val3 = value3
};
rc = syscall(SC_futex, &params);
break;
}
default: {
Syscall::SC_futex_params params {
.userspace_address = userspace_address,
.futex_op = futex_op,
.val = value,
.timeout = timeout,
.userspace_address2 = userspace_address2,
.val3 = value3
};
rc = syscall(SC_futex, &params);
break;
}
}
__RETURN_WITH_ERRNO(rc, rc, -1);
}