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

   1 #include "pthread_impl.h"
   2 #include "syscall.h"
   3 #include "libc.h"
   4
   5 void __cancel()
   6 {
   7         pthread_exit(PTHREAD_CANCELED);
   8 }
   9
  10 /* If __syscall_cp_asm has adjusted the stack pointer, it must provide a
  11  * definition of __cp_cancel to undo those adjustments and call __cancel.
  12  * Otherwise, __cancel provides a definition for __cp_cancel. */
  13
  14 weak_alias(__cancel, __cp_cancel);
  15
  16 long __syscall_cp_asm(volatile void *, syscall_arg_t,
  17                       syscall_arg_t, syscall_arg_t, syscall_arg_t,
  18                       syscall_arg_t, syscall_arg_t, syscall_arg_t);
  19
  20 long __syscall_cp_c(syscall_arg_t nr,
  21                     syscall_arg_t u, syscall_arg_t v, syscall_arg_t w,
  22                     syscall_arg_t x, syscall_arg_t y, syscall_arg_t z)
  23 {
  24         pthread_t self;
  25         long r;
  26
  27         if (!libc.has_thread_pointer || (self = __pthread_self())->canceldisable)
  28                 return __syscall(nr, u, v, w, x, y, z);
  29
  30         r = __syscall_cp_asm(&self->cancel, nr, u, v, w, x, y, z);
  31         if (r==-EINTR && nr!=SYS_close && self->cancel && !self->canceldisable)
  32                 __cancel();
  33         return r;
  34 }
  35
  36 static void _sigaddset(sigset_t *set, int sig)
  37 {
  38         unsigned s = sig-1;
  39         set->__bits[s/8/sizeof *set->__bits] |= 1UL<<(s&8*sizeof *set->__bits-1);
  40 }
  41
  42 static void cancel_handler(int sig, siginfo_t *si, void *ctx)
  43 {
  44         pthread_t self = __pthread_self();
  45         ucontext_t *uc = ctx;
  46         const char *ip = ((char **)&uc->uc_mcontext)[CANCEL_REG_IP];
  47         extern const char __cp_begin[1], __cp_end[1];
  48
  49         a_barrier();
  50         if (!self->cancel || self->canceldisable) return;
  51
  52         _sigaddset(&uc->uc_sigmask, SIGCANCEL);
  53
  54         if (self->cancelasync || ip >= __cp_begin && ip < __cp_end) {
  55                 self->canceldisable = 1;
  56                 pthread_sigmask(SIG_SETMASK, &uc->uc_sigmask, 0);
  57                 __cancel();
  58         }
  59
  60         __syscall(SYS_tkill, self->tid, SIGCANCEL);
  61 }
  62
  63 void __testcancel()
  64 {
  65         if (!libc.has_thread_pointer) return;
  66         pthread_t self = __pthread_self();
  67         if (self->cancel && !self->canceldisable)
  68                 __cancel();
  69 }
  70
  71 static void init_cancellation()
  72 {
  73         struct sigaction sa = {
  74                 .sa_flags = SA_SIGINFO | SA_RESTART,
  75                 .sa_sigaction = cancel_handler
  76         };
  77         sigfillset(&sa.sa_mask);
  78         __libc_sigaction(SIGCANCEL, &sa, 0);
  79 }
  80
  81 int pthread_cancel(pthread_t t)
  82 {
  83         static int init;
  84         if (!init) {
  85                 init_cancellation();
  86                 init = 1;
  87         }
  88         a_store(&t->cancel, 1);
  89         return pthread_kill(t, SIGCANCEL);
  90 }