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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
Download patch file Download diff file Expand all files Collapse all files

34
Userland/Libraries/LibC/serenity.cpp
View file

@ -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);
}

40
Userland/Libraries/LibC/serenity.h
View file

@ -45,10 +45,48 @@ int profiling_disable(pid_t);
#define THREAD_PRIORITY_HIGH 50
#define THREAD_PRIORITY_MAX 99
#define _FUTEX_OP_SHIFT_OP 28
#define _FUTEX_OP_MASK_OP 0xf
#define _FUTEX_OP_SHIFT_CMP 24
#define _FUTEX_OP_MASK_CMP 0xf
#define _FUTEX_OP_SHIFT_OP_ARG 12
#define _FUTEX_OP_MASK_OP_ARG 0xfff
#define _FUTEX_OP_SHIFT_CMP_ARG 0
#define _FUTEX_OP_MASK_CMP_ARG 0xfff
#define FUTEX_OP(op, op_arg, cmp, cmp_arg) \
((((op)&_FUTEX_OP_MASK_OP) << _FUTEX_OP_SHIFT_OP) | (((cmp)&_FUTEX_OP_MASK_CMP) << _FUTEX_OP_SHIFT_CMP) | (((op_arg)&_FUTEX_OP_MASK_OP_ARG) << _FUTEX_OP_SHIFT_OP_ARG) | (((cmp_arg)&_FUTEX_OP_MASK_CMP_ARG) << _FUTEX_OP_SHIFT_CMP_ARG))
#define FUTEX_OP_SET 0
#define FUTEX_OP_ADD 1
#define FUTEX_OP_OR 2
#define FUTEX_OP_ANDN 3
#define FUTEX_OP_XOR 4
#define FUTEX_OP_ARG_SHIFT 8
#define FUTEX_OP_CMP_EQ 0
#define FUTEX_OP_CMP_NE 1
#define FUTEX_OP_CMP_LT 2
#define FUTEX_OP_CMP_LE 3
#define FUTEX_OP_CMP_GT 4
#define FUTEX_OP_CMP_GE 5
#define FUTEX_WAIT 1
#define FUTEX_WAKE 2
int futex(int32_t* userspace_address, int futex_op, int32_t value, const struct timespec* timeout);
#define FUTEX_REQUEUE 3
#define FUTEX_CMP_REQUEUE 4
#define FUTEX_WAKE_OP 5
#define FUTEX_WAIT_BITSET 9
#define FUTEX_WAKE_BITSET 10
#define FUTEX_PRIVATE_FLAG (1 << 7)
#define FUTEX_CLOCK_REALTIME (1 << 8)
#define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
#define FUTEX_BITSET_MATCH_ANY 0xffffffff
int futex(uint32_t* userspace_address, int futex_op, uint32_t value, const struct timespec* timeout, uint32_t* userspace_address2, uint32_t value3);
#define PURGE_ALL_VOLATILE 0x1
#define PURGE_ALL_CLEAN_INODE 0x2

50
Userland/Libraries/LibC/serenity.h.rej Normal file
View file

@ -0,0 +1,50 @@
diff a/Userland/Libraries/LibC/serenity.h b/Userland/Libraries/LibC/serenity.h (rejected hunks)
@@ -55,10 +55,47 @@ int profiling_disable(pid_t);
int set_thread_boost(pid_t tid, int amount);
int set_process_boost(pid_t, int amount);
+#define _FUTEX_OP_SHIFT_OP 28
+#define _FUTEX_OP_MASK_OP 0xf
+#define _FUTEX_OP_SHIFT_CMP 24
+#define _FUTEX_OP_MASK_CMP 0xf
+#define _FUTEX_OP_SHIFT_OP_ARG 12
+#define _FUTEX_OP_MASK_OP_ARG 0xfff
+#define _FUTEX_OP_SHIFT_CMP_ARG 0
+#define _FUTEX_OP_MASK_CMP_ARG 0xfff
+
+#define FUTEX_OP(op, op_arg, cmp, cmp_arg) \
+ ((((op)&_FUTEX_OP_MASK_OP) << _FUTEX_OP_SHIFT_OP) | (((cmp)&_FUTEX_OP_MASK_CMP) << _FUTEX_OP_SHIFT_CMP) | (((op_arg)&_FUTEX_OP_MASK_OP_ARG) << _FUTEX_OP_SHIFT_OP_ARG) | (((cmp_arg)&_FUTEX_OP_MASK_CMP_ARG) << _FUTEX_OP_SHIFT_CMP_ARG))
+
+#define FUTEX_OP_SET 0
+#define FUTEX_OP_ADD 1
+#define FUTEX_OP_OR 2
+#define FUTEX_OP_ANDN 3
+#define FUTEX_OP_XOR 4
+#define FUTEX_OP_ARG_SHIFT 8
+
+#define FUTEX_OP_CMP_EQ 0
+#define FUTEX_OP_CMP_NE 1
+#define FUTEX_OP_CMP_LT 2
+#define FUTEX_OP_CMP_LE 3
+#define FUTEX_OP_CMP_GT 4
+#define FUTEX_OP_CMP_GE 5
+
#define FUTEX_WAIT 1
#define FUTEX_WAKE 2
+#define FUTEX_REQUEUE 3
+#define FUTEX_CMP_REQUEUE 4
+#define FUTEX_WAKE_OP 5
+#define FUTEX_WAIT_BITSET 9
+#define FUTEX_WAKE_BITSET 10
+
+#define FUTEX_PRIVATE_FLAG (1 << 7)
+#define FUTEX_CLOCK_REALTIME (1 << 8)
+#define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
+
+#define FUTEX_BITSET_MATCH_ANY 0xffffffff
-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);
#define PURGE_ALL_VOLATILE 0x1
#define PURGE_ALL_CLEAN_INODE 0x2

4
Userland/Libraries/LibC/sys/types.h
View file

@ -78,7 +78,7 @@ struct utimbuf {
typedef int pthread_t;
typedef int pthread_key_t;
typedef int32_t pthread_once_t;
typedef uint32_t pthread_once_t;
typedef struct __pthread_mutex_t {
uint32_t lock;
@ -93,7 +93,7 @@ typedef struct __pthread_mutexattr_t {
} pthread_mutexattr_t;
typedef struct __pthread_cond_t {
int32_t value;
uint32_t value;
uint32_t previous;
int clockid; // clockid_t
} pthread_cond_t;

21
Userland/Libraries/LibPthread/pthread.cpp
View file

@ -495,12 +495,25 @@ int pthread_cond_destroy(pthread_cond_t*)
return 0;
}
static int futex_wait(uint32_t& futex_addr, uint32_t value, const struct timespec* abstime)
{
int saved_errno = errno;
// NOTE: FUTEX_WAIT takes a relative timeout, so use FUTEX_WAIT_BITSET instead!
int rc = futex(&futex_addr, FUTEX_WAIT_BITSET, value, abstime, nullptr, FUTEX_BITSET_MATCH_ANY);
if (rc < 0 && errno == EAGAIN) {
// If we didn't wait, that's not an error
errno = saved_errno;
rc = 0;
}
return rc;
}
static int cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex, const struct timespec* abstime)
{
i32 value = cond->value;
u32 value = cond->value;
cond->previous = value;
pthread_mutex_unlock(mutex);
int rc = futex(&cond->value, FUTEX_WAIT, value, abstime);
int rc = futex_wait(cond->value, value, abstime);
pthread_mutex_lock(mutex);
return rc;
}
@ -538,7 +551,7 @@ int pthread_cond_signal(pthread_cond_t* cond)
{
u32 value = cond->previous + 1;
cond->value = value;
int rc = futex(&cond->value, FUTEX_WAKE, 1, nullptr);
int rc = futex(&cond->value, FUTEX_WAKE, 1, nullptr, nullptr, 0);
ASSERT(rc == 0);
return 0;
}
@ -547,7 +560,7 @@ int pthread_cond_broadcast(pthread_cond_t* cond)
{
u32 value = cond->previous + 1;
cond->value = value;
int rc = futex(&cond->value, FUTEX_WAKE, INT32_MAX, nullptr);
int rc = futex(&cond->value, FUTEX_WAKE, INT32_MAX, nullptr, nullptr, 0);
ASSERT(rc == 0);
return 0;
}

4
Userland/Libraries/LibPthread/pthread_once.cpp
View file

@ -65,7 +65,7 @@ int pthread_once(pthread_once_t* self, void (*callback)(void))
// anyone.
break;
case State::PERFORMING_WITH_WAITERS:
futex(self, FUTEX_WAKE, INT_MAX, nullptr);
futex(self, FUTEX_WAKE, INT_MAX, nullptr, nullptr, 0);
break;
}
@ -95,7 +95,7 @@ int pthread_once(pthread_once_t* self, void (*callback)(void))
[[fallthrough]];
case State::PERFORMING_WITH_WAITERS:
// Let's wait for it.
futex(self, FUTEX_WAIT, state2, nullptr);
futex(self, FUTEX_WAIT, state2, nullptr, nullptr, 0);
// We have been woken up, but that might have been due to a signal
// or something, so we have to reevaluate. We need acquire ordering
// here for the same reason as above. Hopefully we'll just see