src/thread/pthread_cancel.c

   1 #include <string.h>
   2 #include "pthread_impl.h"
   3 #include "syscall.h"
   4 #include "libc.h"
   5
   6 #ifdef SHARED
   7 #define hidden __attribute__((__visibility__("hidden")))
   8 #else
   9 #define hidden
  10 #endif
  11
  12 hidden 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 hidden weak_alias(__cancel, __cp_cancel);
  26
  27 hidden
  28 long __syscall_cp_asm(volatile void *, syscall_arg_t,
  29                       syscall_arg_t, syscall_arg_t, syscall_arg_t,
  30                       syscall_arg_t, syscall_arg_t, syscall_arg_t);
  31
  32 hidden
  33 long __syscall_cp_c(syscall_arg_t nr,
  34                     syscall_arg_t u, syscall_arg_t v, syscall_arg_t w,
  35                     syscall_arg_t x, syscall_arg_t y, syscall_arg_t z)
  36 {
  37         pthread_t self;
  38         long r;
  39         int st;
  40
  41         if ((st=(self=__pthread_self())->canceldisable)
  42             && (st==PTHREAD_CANCEL_DISABLE || nr==SYS_close))
  43                 return __syscall(nr, u, v, w, x, y, z);
  44
  45         r = __syscall_cp_asm(&self->cancel, nr, u, v, w, x, y, z);
  46         if (r==-EINTR && nr!=SYS_close && self->cancel &&
  47             self->canceldisable != PTHREAD_CANCEL_DISABLE)
  48                 r = __cancel();
  49         return r;
  50 }
  51
  52 static void _sigaddset(sigset_t *set, int sig)
  53 {
  54         unsigned s = sig-1;
  55         set->__bits[s/8/sizeof *set->__bits] |= 1UL<<(s&8*sizeof *set->__bits-1);
  56 }
  57
  58 static void cancel_handler(int sig, siginfo_t *si, void *ctx)
  59 {
  60         pthread_t self = __pthread_self();
  61         ucontext_t *uc = ctx;
  62         const char *ip = ((char **)&uc->uc_mcontext)[CANCEL_REG_IP];
  63         hidden extern const char __cp_begin[1], __cp_end[1];
  64
  65         a_barrier();
  66         if (!self->cancel || self->canceldisable == PTHREAD_CANCEL_DISABLE) return;
  67
  68         _sigaddset(&uc->uc_sigmask, SIGCANCEL);
  69
  70         if (self->cancelasync || ip >= __cp_begin && ip < __cp_end) {
  71                 ((char **)&uc->uc_mcontext)[CANCEL_REG_IP] = (char *)__cp_cancel;
  72                 return;
  73         }
  74
  75         __syscall(SYS_tkill, self->tid, SIGCANCEL);
  76 }
  77
  78 void __testcancel()
  79 {
  80         pthread_t self = __pthread_self();
  81         if (self->cancel && !self->canceldisable)
  82                 __cancel();
  83 }
  84
  85 static void init_cancellation()
  86 {
  87         struct sigaction sa = {
  88                 .sa_flags = SA_SIGINFO | SA_RESTART,
  89                 .sa_sigaction = cancel_handler
  90         };
  91         memset(&sa.sa_mask, -1, _NSIG/8);
  92         __libc_sigaction(SIGCANCEL, &sa, 0);
  93 }
  94
  95 int pthread_cancel(pthread_t t)
  96 {
  97         static int init;
  98         if (!init) {
  99                 init_cancellation();
 100                 init = 1;
 101         }
 102         a_store(&t->cancel, 1);
 103         return pthread_kill(t, SIGCANCEL);
 104 }