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 __attribute__((__visibility__("hidden")))
   8 long __cancel(), __syscall_cp_asm(), __syscall_cp_c();
   9
  10 long __cancel()
  11 {
  12         pthread_t self = __pthread_self();
  13         if (self->canceldisable == PTHREAD_CANCEL_ENABLE || self->cancelasync)
  14                 pthread_exit(PTHREAD_CANCELED);
  15         self->canceldisable = PTHREAD_CANCEL_DISABLE;
  16         return -ECANCELED;
  17 }
  18
  19 long __syscall_cp_asm(volatile void *, syscall_arg_t,
  20                       syscall_arg_t, syscall_arg_t, syscall_arg_t,
  21                       syscall_arg_t, syscall_arg_t, syscall_arg_t);
  22
  23 long __syscall_cp_c(syscall_arg_t nr,
  24                     syscall_arg_t u, syscall_arg_t v, syscall_arg_t w,
  25                     syscall_arg_t x, syscall_arg_t y, syscall_arg_t z)
  26 {
  27         pthread_t self;
  28         long r;
  29         int st;
  30
  31         if ((st=(self=__pthread_self())->canceldisable)
  32             && (st==PTHREAD_CANCEL_DISABLE || nr==SYS_close))
  33                 return __syscall(nr, u, v, w, x, y, z);
  34
  35         r = __syscall_cp_asm(&self->cancel, nr, u, v, w, x, y, z);
  36         if (r==-EINTR && nr!=SYS_close && self->cancel &&
  37             self->canceldisable != PTHREAD_CANCEL_DISABLE)
  38                 r = __cancel();
  39         return r;
  40 }
  41
  42 static void _sigaddset(sigset_t *set, int sig)
  43 {
  44         unsigned s = sig-1;
  45         set->__bits[s/8/sizeof *set->__bits] |= 1UL<<(s&8*sizeof *set->__bits-1);
  46 }
  47
  48 __attribute__((__visibility__("hidden")))
  49 extern const char __cp_begin[1], __cp_end[1], __cp_cancel[1];
  50
  51 static void cancel_handler(int sig, siginfo_t *si, void *ctx)
  52 {
  53         pthread_t self = __pthread_self();
  54         ucontext_t *uc = ctx;
  55         uintptr_t pc = uc->uc_mcontext.MC_PC;
  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 || pc >= (uintptr_t)__cp_begin && pc < (uintptr_t)__cp_end) {
  63                 uc->uc_mcontext.MC_PC = (uintptr_t)__cp_cancel;
  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() && !t->cancelasync) return 0;
  96         return pthread_kill(t, SIGCANCEL);
  97 }