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 #ifdef SHARED
   8 __attribute__((__visibility__("hidden")))
   9 #endif
  10 long __cancel(), __cp_cancel(), __syscall_cp_asm(), __syscall_cp_c();
  11
  12 long __cancel()
  13 {
  14         pthread_t self = __pthread_self();
  15         if (self->canceldisable == PTHREAD_CANCEL_ENABLE || self->cancelasync)
  16                 pthread_exit(PTHREAD_CANCELED);
  17         self->canceldisable = PTHREAD_CANCEL_DISABLE;
  18         return -ECANCELED;
  19 }
  20
  21 /* If __syscall_cp_asm has adjusted the stack pointer, it must provide a
  22  * definition of __cp_cancel to undo those adjustments and call __cancel.
  23  * Otherwise, __cancel provides a definition for __cp_cancel. */
  24
  25 weak_alias(__cancel, __cp_cancel);
  26
  27 long __syscall_cp_asm(volatile void *, syscall_arg_t,
  28                       syscall_arg_t, syscall_arg_t, syscall_arg_t,
  29                       syscall_arg_t, syscall_arg_t, syscall_arg_t);
  30
  31 long __syscall_cp_c(syscall_arg_t nr,
  32                     syscall_arg_t u, syscall_arg_t v, syscall_arg_t w,
  33                     syscall_arg_t x, syscall_arg_t y, syscall_arg_t z)
  34 {
  35         pthread_t self;
  36         long r;
  37         int st;
  38
  39         if ((st=(self=__pthread_self())->canceldisable)
  40             && (st==PTHREAD_CANCEL_DISABLE || nr==SYS_close))
  41                 return __syscall(nr, u, v, w, x, y, z);
  42
  43         r = __syscall_cp_asm(&self->cancel, nr, u, v, w, x, y, z);
  44         if (r==-EINTR && nr!=SYS_close && self->cancel &&
  45             self->canceldisable != PTHREAD_CANCEL_DISABLE)
  46                 r = __cancel();
  47         return r;
  48 }
  49
  50 static void _sigaddset(sigset_t *set, int sig)
  51 {
  52         unsigned s = sig-1;
  53         set->__bits[s/8/sizeof *set->__bits] |= 1UL<<(s&8*sizeof *set->__bits-1);
  54 }
  55
  56 #ifdef SHARED
  57 __attribute__((__visibility__("hidden")))
  58 #endif
  59 extern const char __cp_begin[1], __cp_end[1];
  60
  61 static void cancel_handler(int sig, siginfo_t *si, void *ctx)
  62 {
  63         pthread_t self = __pthread_self();
  64         ucontext_t *uc = ctx;
  65         uintptr_t pc = uc->uc_mcontext.MC_PC;
  66
  67         a_barrier();
  68         if (!self->cancel || self->canceldisable == PTHREAD_CANCEL_DISABLE) return;
  69
  70         _sigaddset(&uc->uc_sigmask, SIGCANCEL);
  71
  72         if (self->cancelasync || pc >= (uintptr_t)__cp_begin && pc < (uintptr_t)__cp_end) {
  73                 uc->uc_mcontext.MC_PC = (uintptr_t)__cp_cancel;
  74                 return;
  75         }
  76
  77         __syscall(SYS_tkill, self->tid, SIGCANCEL);
  78 }
  79
  80 void __testcancel()
  81 {
  82         pthread_t self = __pthread_self();
  83         if (self->cancel && !self->canceldisable)
  84                 __cancel();
  85 }
  86
  87 static void init_cancellation()
  88 {
  89         struct sigaction sa = {
  90                 .sa_flags = SA_SIGINFO | SA_RESTART,
  91                 .sa_sigaction = cancel_handler
  92         };
  93         memset(&sa.sa_mask, -1, _NSIG/8);
  94         __libc_sigaction(SIGCANCEL, &sa, 0);
  95 }
  96
  97 int pthread_cancel(pthread_t t)
  98 {
  99         static int init;
 100         if (!init) {
 101                 init_cancellation();
 102                 init = 1;
 103         }
 104         a_store(&t->cancel, 1);
 105         return pthread_kill(t, SIGCANCEL);
 106 }