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(), __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 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 ((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 #ifdef SHARED
  51 __attribute__((__visibility__("hidden")))
  52 #endif
  53 extern const char __cp_begin[1], __cp_end[1], __cp_cancel[1];
  54
  55 static void cancel_handler(int sig, siginfo_t *si, void *ctx)
  56 {
  57         pthread_t self = __pthread_self();
  58         ucontext_t *uc = ctx;
  59         uintptr_t pc = uc->uc_mcontext.MC_PC;
  60
  61         a_barrier();
  62         if (!self->cancel || self->canceldisable == PTHREAD_CANCEL_DISABLE) return;
  63
  64         _sigaddset(&uc->uc_sigmask, SIGCANCEL);
  65
  66         if (self->cancelasync || pc >= (uintptr_t)__cp_begin && pc < (uintptr_t)__cp_end) {
  67                 uc->uc_mcontext.MC_PC = (uintptr_t)__cp_cancel;
  68                 return;
  69         }
  70
  71         __syscall(SYS_tkill, self->tid, SIGCANCEL);
  72 }
  73
  74 void __testcancel()
  75 {
  76         pthread_t self = __pthread_self();
  77         if (self->cancel && !self->canceldisable)
  78                 __cancel();
  79 }
  80
  81 static void init_cancellation()
  82 {
  83         struct sigaction sa = {
  84                 .sa_flags = SA_SIGINFO | SA_RESTART,
  85                 .sa_sigaction = cancel_handler
  86         };
  87         memset(&sa.sa_mask, -1, _NSIG/8);
  88         __libc_sigaction(SIGCANCEL, &sa, 0);
  89 }
  90
  91 int pthread_cancel(pthread_t t)
  92 {
  93         static int init;
  94         if (!init) {
  95                 init_cancellation();
  96                 init = 1;
  97         }
  98         a_store(&t->cancel, 1);
  99         return pthread_kill(t, SIGCANCEL);
 100 }