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

   1 #define _GNU_SOURCE
   2 #include <string.h>
   3 #include "pthread_impl.h"
   4 #include "syscall.h"
   5 #include "libc.h"
   6
   7 hidden long __cancel(), __syscall_cp_asm(), __syscall_cp_c();
   8
   9 long __cancel()
  10 {
  11         pthread_t self = __pthread_self();
  12         if (self->canceldisable == PTHREAD_CANCEL_ENABLE || self->cancelasync)
  13                 pthread_exit(PTHREAD_CANCELED);
  14         self->canceldisable = PTHREAD_CANCEL_DISABLE;
  15         return -ECANCELED;
  16 }
  17
  18 long __syscall_cp_asm(volatile void *, syscall_arg_t,
  19                       syscall_arg_t, syscall_arg_t, syscall_arg_t,
  20                       syscall_arg_t, syscall_arg_t, syscall_arg_t);
  21
  22 long __syscall_cp_c(syscall_arg_t nr,
  23                     syscall_arg_t u, syscall_arg_t v, syscall_arg_t w,
  24                     syscall_arg_t x, syscall_arg_t y, syscall_arg_t z)
  25 {
  26         pthread_t self;
  27         long r;
  28         int st;
  29
  30         if ((st=(self=__pthread_self())->canceldisable)
  31             && (st==PTHREAD_CANCEL_DISABLE || nr==SYS_close))
  32                 return __syscall(nr, u, v, w, x, y, z);
  33
  34         r = __syscall_cp_asm(&self->cancel, nr, u, v, w, x, y, z);
  35         if (r==-EINTR && nr!=SYS_close && self->cancel &&
  36             self->canceldisable != PTHREAD_CANCEL_DISABLE)
  37                 r = __cancel();
  38         return r;
  39 }
  40
  41 static void _sigaddset(sigset_t *set, int sig)
  42 {
  43         unsigned s = sig-1;
  44         set->__bits[s/8/sizeof *set->__bits] |= 1UL<<(s&8*sizeof *set->__bits-1);
  45 }
  46
  47 extern hidden const char __cp_begin[1], __cp_end[1], __cp_cancel[1];
  48
  49 static void cancel_handler(int sig, siginfo_t *si, void *ctx)
  50 {
  51         pthread_t self = __pthread_self();
  52         ucontext_t *uc = ctx;
  53         uintptr_t pc = uc->uc_mcontext.MC_PC;
  54
  55         a_barrier();
  56         if (!self->cancel || self->canceldisable == PTHREAD_CANCEL_DISABLE) return;
  57
  58         _sigaddset(&uc->uc_sigmask, SIGCANCEL);
  59
  60         if (self->cancelasync || pc >= (uintptr_t)__cp_begin && pc < (uintptr_t)__cp_end) {
  61                 uc->uc_mcontext.MC_PC = (uintptr_t)__cp_cancel;
  62 #ifdef CANCEL_GOT
  63                 uc->uc_mcontext.MC_GOT = CANCEL_GOT;
  64 #endif
  65                 return;
  66         }
  67
  68         __syscall(SYS_tkill, self->tid, SIGCANCEL);
  69 }
  70
  71 void __testcancel()
  72 {
  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         if (t == pthread_self()) {
  97                 if (t->canceldisable == PTHREAD_CANCEL_ENABLE && t->cancelasync)
  98                         pthread_exit(PTHREAD_CANCELED);
  99                 return 0;
 100         }
 101         return pthread_kill(t, SIGCANCEL);
 102 }