nsz Git - musl/blob - src/thread/pthread_cancel.c

   1 #include "pthread_impl.h"
   2 #include "syscall.h"
   3 #include "libc.h"
   4
   5 long __cancel()
   6 {
   7         pthread_t self = __pthread_self();
   8         if (self->canceldisable == PTHREAD_CANCEL_ENABLE || self->cancelasync)
   9                 pthread_exit(PTHREAD_CANCELED);
  10         self->canceldisable = PTHREAD_CANCEL_DISABLE;
  11         return -ECANCELED;
  12 }
  13
  14 /* If __syscall_cp_asm has adjusted the stack pointer, it must provide a
  15  * definition of __cp_cancel to undo those adjustments and call __cancel.
  16  * Otherwise, __cancel provides a definition for __cp_cancel. */
  17
  18 weak_alias(__cancel, __cp_cancel);
  19
  20 long __syscall_cp_asm(volatile void *, syscall_arg_t,
  21                       syscall_arg_t, syscall_arg_t, syscall_arg_t,
  22                       syscall_arg_t, syscall_arg_t, syscall_arg_t);
  23
  24 long __syscall_cp_c(syscall_arg_t nr,
  25                     syscall_arg_t u, syscall_arg_t v, syscall_arg_t w,
  26                     syscall_arg_t x, syscall_arg_t y, syscall_arg_t z)
  27 {
  28         pthread_t self;
  29         long r;
  30         int st;
  31
  32         if (!libc.has_thread_pointer || (st=(self=__pthread_self())->canceldisable)
  33             && (st==PTHREAD_CANCEL_DISABLE || nr==SYS_close))
  34                 return __syscall(nr, u, v, w, x, y, z);
  35
  36         r = __syscall_cp_asm(&self->cancel, nr, u, v, w, x, y, z);
  37         if (r==-EINTR && nr!=SYS_close && self->cancel &&
  38             self->canceldisable != PTHREAD_CANCEL_DISABLE)
  39                 r = __cancel();
  40         return r;
  41 }
  42
  43 static void _sigaddset(sigset_t *set, int sig)
  44 {
  45         unsigned s = sig-1;
  46         set->__bits[s/8/sizeof *set->__bits] |= 1UL<<(s&8*sizeof *set->__bits-1);
  47 }
  48
  49 static void cancel_handler(int sig, siginfo_t *si, void *ctx)
  50 {
  51         pthread_t self = __pthread_self();
  52         ucontext_t *uc = ctx;
  53         const char *ip = ((char **)&uc->uc_mcontext)[CANCEL_REG_IP];
  54         extern const char __cp_begin[1], __cp_end[1];
  55
  56         a_barrier();
  57         if (!self->cancel || self->canceldisable == PTHREAD_CANCEL_DISABLE) return;
  58
  59         _sigaddset(&uc->uc_sigmask, SIGCANCEL);
  60
  61         if (self->cancelasync || ip >= __cp_begin && ip < __cp_end) {
  62                 ((char **)&uc->uc_mcontext)[CANCEL_REG_IP] = (char *)__cp_cancel;
  63                 return;
  64         }
  65
  66         __syscall(SYS_tkill, self->tid, SIGCANCEL);
  67 }
  68
  69 void __testcancel()
  70 {
  71         if (!libc.has_thread_pointer) return;
  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         sigfillset(&sa.sa_mask);
  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         return pthread_kill(t, SIGCANCEL);
  96 }