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Make more improvements to threading support

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- fix rare thread exit race condition on openbsd
- pthread_getattr_np() now supplies detached status
- child threads may now pthread_join() the main thread
- introduce sigandset(), sigorset(), and sigisemptyset()
- introduce pthread_cleanup_push() and pthread_cleanup_pop()
This commit is contained in:
Justine Tunney 2022-10-08 23:54:05 -07:00
parent 38df0a4186
commit 4a6fd3d910
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GPG key ID: BE714B4575D6E328
52 changed files with 586 additions and 241 deletions
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41
libc/runtime/clone.c
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@ -240,12 +240,14 @@ static wontreturn void FreebsdThreadMain(void *p) {
// we no longer use the stack after this point
// void thr_exit(%rdi = long *state);
asm volatile("movl\t$0,%0\n\t" // *wt->ztid = 0
"syscall\n\t" // _umtx_op()
"movl\t$431,%%eax\n\t" // thr_exit()
"xor\t%%edi,%%edi\n\t"
"syscall"
"syscall\n\t" // _umtx_op(wt->ztid, WAKE, INT_MAX)
"movl\t$431,%%eax\n\t" // thr_exit(long *nonzeroes_and_wake)
"xor\t%%edi,%%edi\n\t" // sad we can't use this free futex op
"syscall\n\t" // exit1() fails if thread is orphaned
"movl\t$1,%%eax\n\t" // exit()
"syscall" //
: "=m"(*wt->ztid)
: "a"(454), "D"(wt->ztid), "S"(UMTX_OP_WAKE)
: "a"(454), "D"(wt->ztid), "S"(UMTX_OP_WAKE), "d"(INT_MAX)
: "rcx", "r8", "r9", "r10", "r11", "memory");
notpossible;
}
@ -289,15 +291,6 @@ static int CloneFreebsd(int (*func)(void *, int), char *stk, size_t stksz,
////////////////////////////////////////////////////////////////////////////////
// OPEN BESIYATA DISHMAYA
static void *oldrsp;
__attribute__((__constructor__)) static void OpenbsdGetSafeRsp(void) {
// main thread stack should never be freed during process lifetime. we
// won't actually change this stack below. we just need need a place
// where threads can park RSP for a few instructions while dying.
oldrsp = __builtin_frame_address(0);
}
// we can't use address sanitizer because:
// 1. __asan_handle_no_return wipes stack [todo?]
noasan static wontreturn void OpenbsdThreadMain(void *p) {
@ -305,21 +298,15 @@ noasan static wontreturn void OpenbsdThreadMain(void *p) {
*wt->ptid = wt->tid;
*wt->ctid = wt->tid;
wt->func(wt->arg, wt->tid);
// we no longer use the stack after this point. however openbsd
// validates the rsp register too so a race condition can still
// happen if the parent tries to free the stack. we'll solve it
// by simply changing rsp back to the old value before exiting!
// although ideally there should be a better solution.
//
// void __threxit(%rdi = int32_t *notdead);
asm volatile("mov\t%2,%%rsp\n\t"
"movl\t$0,(%%rdi)\n\t" // *wt->ztid = 0
"syscall\n\t" // futex()
"mov\t$302,%%eax\n\t" // threxit()
asm volatile("mov\t%2,%%rsp\n\t" // so syscall can validate stack exists
"movl\t$0,(%%rdi)\n\t" // *wt->ztid = 0 (old stack now free'd)
"syscall\n\t" // futex(int*, op, val) will wake wait0
"xor\t%%edi,%%edi\n\t" // so kernel doesn't write to old stack
"mov\t$302,%%eax\n\t" // __threxit(int *notdead) doesn't wake
"syscall"
: "=m"(*wt->ztid)
: "a"(83), "m"(oldrsp), "D"(wt->ztid), "S"(FUTEX_WAKE),
"d"(INT_MAX)
: "a"(83), "m"(__oldstack), "D"(wt->ztid),
"S"(2 /* FUTEX_WAKE */), "d"(INT_MAX)
: "rcx", "r11", "memory");
notpossible;
}