this repo has no description
Add a linux_futex syscall that doesn't modify errno
This fixes some crashes due to accessing errno (which is per-thread)
after the thread had already been terminated. This was due to us having
to unguard an FD when a thread dies, which requires us to take a lock.
+14
-8
+5
src/kernel/emulation/linux/ext/futex.c
+5
src/kernel/emulation/linux/ext/futex.c
···
21
21
return rv;
22
22
}
23
23
24
+
VISIBLE
25
+
int __linux_futex_reterr(int *uaddr, int op, int val, const struct timespec *timeout, int *uaddr2, int val3) {
26
+
int rv = LINUX_SYSCALL(__NR_futex, uaddr, op, val, timeout, uaddr2, val3);
27
+
return (rv < 0) ? errno_linux_to_bsd(rv) : rv;
28
+
};
+1
src/kernel/emulation/linux/ext/futex.h
+1
src/kernel/emulation/linux/ext/futex.h
+4
-4
src/libsimple/src/lock.c
+4
-4
src/libsimple/src/lock.c
···
31
31
#include <sys/syscall.h>
32
32
#include <unistd.h>
33
33
#elif LIBSIMPLE_DARLING
34
-
extern int __linux_futex(int* uaddr, int op, int val, const struct timespec* timeout, int* uaddr2, int val3);
34
+
extern int __linux_futex_reterr(int* uaddr, int op, int val, const struct timespec* timeout, int* uaddr2, int val3);
35
35
#endif
36
36
37
37
#if LIBSIMPLE_DARLING
38
-
#define linux_futex __linux_futex
38
+
#define linux_futex __linux_futex_reterr
39
39
#else // !LIBSIMPLE_DARLING
40
-
static int linux_futex(int* uaddr, int op, int val, const struct timespec* timeout, int* uaddr2, int val3) {
40
+
static void linux_futex(int* uaddr, int op, int val, const struct timespec* timeout, int* uaddr2, int val3) {
41
41
#if LIBSIMPLE_LINUX
42
-
return syscall(SYS_futex, uaddr, op, val, timeout, uaddr2, val3);
42
+
syscall(SYS_futex, uaddr, op, val, timeout, uaddr2, val3);
43
43
#else
44
44
#error linux_futex not implemented for this platform
45
45
#endif
+4
-4
src/xtrace/lock.c
+4
-4
src/xtrace/lock.c
···
70
70
xtrace_lock_debug("going to wait");
71
71
// do the actual sleeping
72
72
// we expect `xtrace_lock_state_locked_contended` because we don't want to sleep if it's not contended
73
-
__linux_futex(&lock->state, FUTEX_WAIT, xtrace_lock_state_locked_contended, NULL, 0, 0);
73
+
__linux_futex_reterr(&lock->state, FUTEX_WAIT, xtrace_lock_state_locked_contended, NULL, 0, 0);
74
74
xtrace_lock_debug("awoken");
75
75
}
76
76
···
95
95
// if it was previously contended, then we need to wake someone up
96
96
if (prev == xtrace_lock_state_locked_contended) {
97
97
xtrace_lock_debug("waking someone up");
98
-
__linux_futex(&lock->state, FUTEX_WAKE, 1, NULL, 0, 0);
98
+
__linux_futex_reterr(&lock->state, FUTEX_WAKE, 1, NULL, 0, 0);
99
99
}
100
100
};
101
101
···
152
152
case xtrace_once_state_triggered_contended: {
153
153
xtrace_once_debug("waking up all waiters...");
154
154
// otherwise, we have to wake someone up
155
-
__linux_futex(&once->state, FUTEX_WAKE, INT_MAX, NULL, 0, 0);
155
+
__linux_futex_reterr(&once->state, FUTEX_WAKE, INT_MAX, NULL, 0, 0);
156
156
} break;
157
157
}
158
158
···
184
184
// somebody is already performing the callback and there are already waiters;
185
185
// let's wait
186
186
xtrace_once_debug("someone is already performing the callback with waiters; going to wait...");
187
-
__linux_futex(&once->state, FUTEX_WAIT, prev, NULL, 0, 0);
187
+
__linux_futex_reterr(&once->state, FUTEX_WAIT, prev, NULL, 0, 0);
188
188
189
189
xtrace_once_debug("woken up");
190
190