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