nsz Git - musl/blob - src/thread/pthread_cancel.c

   1 #include <string.h>
   2 #include "pthread_impl.h"
   3 #include "syscall.h"
   4 #include "libc.h"
   5
   6 #ifdef SHARED
   7 __attribute__((__visibility__("hidden")))
   8 #endif
   9 long __cancel(), __cp_cancel(), __syscall_cp_asm(), __syscall_cp_c();
  10
  11 long __cancel()
  12 {
  13         pthread_t self = __pthread_self();
  14         if (self->canceldisable == PTHREAD_CANCEL_ENABLE || self->cancelasync)
  15                 pthread_exit(PTHREAD_CANCELED);
  16         self->canceldisable = PTHREAD_CANCEL_DISABLE;
  17         return -ECANCELED;
  18 }
  19
  20 /* If __syscall_cp_asm has adjusted the stack pointer, it must provide a
  21  * definition of __cp_cancel to undo those adjustments and call __cancel.
  22  * Otherwise, __cancel provides a definition for __cp_cancel. */
  23
  24 weak_alias(__cancel, __cp_cancel);
  25
  26 long __syscall_cp_asm(volatile void *, syscall_arg_t,
  27                       syscall_arg_t, syscall_arg_t, syscall_arg_t,
  28                       syscall_arg_t, syscall_arg_t, syscall_arg_t);
  29
  30 long __syscall_cp_c(syscall_arg_t nr,
  31                     syscall_arg_t u, syscall_arg_t v, syscall_arg_t w,
  32                     syscall_arg_t x, syscall_arg_t y, syscall_arg_t z)
  33 {
  34         pthread_t self;
  35         long r;
  36         int st;
  37
  38         if ((st=(self=__pthread_self())->canceldisable)
  39             && (st==PTHREAD_CANCEL_DISABLE || nr==SYS_close))
  40                 return __syscall(nr, u, v, w, x, y, z);
  41
  42         r = __syscall_cp_asm(&self->cancel, nr, u, v, w, x, y, z);
  43         if (r==-EINTR && nr!=SYS_close && self->cancel &&
  44             self->canceldisable != PTHREAD_CANCEL_DISABLE)
  45                 r = __cancel();
  46         return r;
  47 }
  48
  49 static void _sigaddset(sigset_t *set, int sig)
  50 {
  51         unsigned s = sig-1;
  52         set->__bits[s/8/sizeof *set->__bits] |= 1UL<<(s&8*sizeof *set->__bits-1);
  53 }
  54
  55 #ifdef SHARED
  56 __attribute__((__visibility__("hidden")))
  57 #endif
  58 extern const char __cp_begin[1], __cp_end[1];
  59
  60 static void cancel_handler(int sig, siginfo_t *si, void *ctx)
  61 {
  62         pthread_t self = __pthread_self();
  63         ucontext_t *uc = ctx;
  64         const char *ip = ((char **)&uc->uc_mcontext)[CANCEL_REG_IP];
  65
  66         a_barrier();
  67         if (!self->cancel || self->canceldisable == PTHREAD_CANCEL_DISABLE) return;
  68
  69         _sigaddset(&uc->uc_sigmask, SIGCANCEL);
  70
  71         if (self->cancelasync || ip >= __cp_begin && ip < __cp_end) {
  72                 ((char **)&uc->uc_mcontext)[CANCEL_REG_IP] = (char *)__cp_cancel;
  73                 return;
  74         }
  75
  76         __syscall(SYS_tkill, self->tid, SIGCANCEL);
  77 }
  78
  79 void __testcancel()
  80 {
  81         pthread_t self = __pthread_self();
  82         if (self->cancel && !self->canceldisable)
  83                 __cancel();
  84 }
  85
  86 static void init_cancellation()
  87 {
  88         struct sigaction sa = {
  89                 .sa_flags = SA_SIGINFO | SA_RESTART,
  90                 .sa_sigaction = cancel_handler
  91         };
  92         memset(&sa.sa_mask, -1, _NSIG/8);
  93         __libc_sigaction(SIGCANCEL, &sa, 0);
  94 }
  95
  96 int pthread_cancel(pthread_t t)
  97 {
  98         static int init;
  99         if (!init) {
 100                 init_cancellation();
 101                 init = 1;
 102         }
 103         a_store(&t->cancel, 1);
 104         return pthread_kill(t, SIGCANCEL);
 105 }