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Implement FUTEX_WAIT_BITSET and FUTEX_WAKE_BITSET #2775

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Implement FUTEX_WAIT_BITSET and FUTEX_WAKE_BITSET #2775

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58 changes: 49 additions & 9 deletions kernel/futex.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,15 @@
#define FUTEX_WAIT_ 0
#define FUTEX_WAKE_ 1
#define FUTEX_REQUEUE_ 3
#define FUTEX_WAIT_BITSET_ 9
#define FUTEX_WAKE_BITSET_ 10
#define FUTEX_PRIVATE_FLAG_ 128
#define FUTEX_CMD_MASK_ ~(FUTEX_PRIVATE_FLAG_)
#define FUTEX_CLOCK_REALTIME_ 256
// FUTEX_CLOCK_REALTIME selects the clock for FUTEX_WAIT_BITSET's absolute
// timeout; like FUTEX_PRIVATE_FLAG it is a modifier, not part of the command,
// so it has to come off before the switch.
#define FUTEX_CMD_MASK_ ~(FUTEX_PRIVATE_FLAG_ | FUTEX_CLOCK_REALTIME_)
#define FUTEX_BITSET_MATCH_ANY_ 0xffffffff

struct futex {
atomic_uint refcount;
Expand All @@ -18,6 +25,7 @@ struct futex_wait {
cond_t cond;
struct futex *futex; // will be changed by a requeue
struct list queue;
dword_t bitset; // FUTEX_BITSET_MATCH_ANY_ for a plain FUTEX_WAIT
};

#define FUTEX_HASH_BITS 12
Expand Down Expand Up @@ -90,7 +98,7 @@ static int futex_load(struct futex *futex, dword_t *out) {
return 0;
}

static int futex_wait(addr_t uaddr, dword_t val, struct timespec *timeout) {
static int futex_wait(addr_t uaddr, dword_t val, struct timespec *timeout, dword_t bitset) {
struct futex *futex = futex_get(uaddr);
int err = 0;
dword_t tmp;
Expand All @@ -102,6 +110,7 @@ static int futex_wait(addr_t uaddr, dword_t val, struct timespec *timeout) {
struct futex_wait wait;
wait.cond = COND_INITIALIZER;
wait.futex = futex;
wait.bitset = bitset;
list_add_tail(&futex->queue, &wait.queue);
err = wait_for(&wait.cond, &futex_lock, timeout);
futex = wait.futex;
Expand All @@ -112,14 +121,19 @@ static int futex_wait(addr_t uaddr, dword_t val, struct timespec *timeout) {
return err;
}

static int futex_wakelike(int op, addr_t uaddr, dword_t wake_max, dword_t requeue_max, addr_t requeue_addr) {
static int futex_wakelike(int op, addr_t uaddr, dword_t wake_max, dword_t requeue_max, addr_t requeue_addr, dword_t bitset) {
struct futex *futex = futex_get(uaddr);

struct futex_wait *wait, *tmp;
unsigned woken = 0;
list_for_each_entry_safe(&futex->queue, wait, tmp, queue) {
if (woken >= wake_max)
break;
// A waiter only wakes if its mask overlaps the waker's. Plain
// FUTEX_WAIT/FUTEX_WAKE both use FUTEX_BITSET_MATCH_ANY_, so they are
// unaffected.
if ((wait->bitset & bitset) == 0)
continue;
notify(&wait->cond);
list_remove(&wait->queue);
woken++;
Expand Down Expand Up @@ -149,31 +163,57 @@ static int futex_wakelike(int op, addr_t uaddr, dword_t wake_max, dword_t requeu
}

int futex_wake(addr_t uaddr, dword_t wake_max) {
return futex_wakelike(FUTEX_WAKE_, uaddr, wake_max, 0, 0);
return futex_wakelike(FUTEX_WAKE_, uaddr, wake_max, 0, 0, FUTEX_BITSET_MATCH_ANY_);
}

dword_t sys_futex(addr_t uaddr, dword_t op, dword_t val, addr_t timeout_or_val2, addr_t uaddr2, dword_t val3) {
if (!(op & FUTEX_PRIVATE_FLAG_)) {
STRACE("!FUTEX_PRIVATE ");
}
struct timespec timeout = {0};
if ((op & FUTEX_CMD_MASK_) == FUTEX_WAIT_ && timeout_or_val2) {
int cmd = op & FUTEX_CMD_MASK_;
if ((cmd == FUTEX_WAIT_ || cmd == FUTEX_WAIT_BITSET_) && timeout_or_val2) {
struct timespec_ timeout_;
if (user_get(timeout_or_val2, timeout_))
return _EFAULT;
timeout.tv_sec = timeout_.sec;
timeout.tv_nsec = timeout_.nsec;
if (cmd == FUTEX_WAIT_BITSET_) {
// FUTEX_WAIT takes a relative timeout, FUTEX_WAIT_BITSET an
// absolute one -- against CLOCK_REALTIME when FUTEX_CLOCK_REALTIME
// is set, CLOCK_MONOTONIC otherwise. wait_for wants it relative.
struct timespec now;
clock_gettime(op & FUTEX_CLOCK_REALTIME_ ? CLOCK_REALTIME : CLOCK_MONOTONIC, &now);
timeout.tv_sec -= now.tv_sec;
timeout.tv_nsec -= now.tv_nsec;
if (timeout.tv_nsec < 0) {
timeout.tv_nsec += 1000000000;
timeout.tv_sec--;
}
if (timeout.tv_sec < 0)
timeout.tv_sec = timeout.tv_nsec = 0; // already expired
}
}
switch (op & FUTEX_CMD_MASK_) {
switch (cmd) {
case FUTEX_WAIT_:
STRACE("futex(FUTEX_WAIT, %#x, %d, 0x%x {%ds %dns}) = ...\n", uaddr, val, timeout_or_val2, timeout.tv_sec, timeout.tv_nsec);
return futex_wait(uaddr, val, timeout_or_val2 ? &timeout : NULL);
return futex_wait(uaddr, val, timeout_or_val2 ? &timeout : NULL, FUTEX_BITSET_MATCH_ANY_);
case FUTEX_WAIT_BITSET_:
STRACE("futex(FUTEX_WAIT_BITSET, %#x, %d, 0x%x {%ds %dns}, %#x) = ...\n", uaddr, val, timeout_or_val2, timeout.tv_sec, timeout.tv_nsec, val3);
if (val3 == 0)
return _EINVAL;
return futex_wait(uaddr, val, timeout_or_val2 ? &timeout : NULL, val3);
case FUTEX_WAKE_:
STRACE("futex(FUTEX_WAKE, %#x, %d)", uaddr, val);
return futex_wakelike(op & FUTEX_CMD_MASK_, uaddr, val, 0, 0);
return futex_wakelike(cmd, uaddr, val, 0, 0, FUTEX_BITSET_MATCH_ANY_);
case FUTEX_WAKE_BITSET_:
STRACE("futex(FUTEX_WAKE_BITSET, %#x, %d, %#x)", uaddr, val, val3);
if (val3 == 0)
return _EINVAL;
return futex_wakelike(FUTEX_WAKE_, uaddr, val, 0, 0, val3);
case FUTEX_REQUEUE_:
STRACE("futex(FUTEX_REQUEUE, %#x, %d, %#x)", uaddr, val, uaddr2);
return futex_wakelike(op & FUTEX_CMD_MASK_, uaddr, val, timeout_or_val2, uaddr2);
return futex_wakelike(cmd, uaddr, val, timeout_or_val2, uaddr2, FUTEX_BITSET_MATCH_ANY_);
}
STRACE("futex(%#x, %d, %d, timeout=%#x, %#x, %d) ", uaddr, op, val, timeout_or_val2, uaddr2, val3);
FIXME("unsupported futex operation %d", op);
Expand Down
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