src/thread/pthread_cancel.c

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