man3/pthread_cleanup_push_defer_np.3

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  26 .TH PTHREAD_CLEANUP_PUSH_DEFER_NP 3 2017-09-15 "Linux" "Linux Programmer's Manual"
  27 .SH NAME
  28 pthread_cleanup_push_defer_np, pthread_cleanup_pop_restore_np \- push and pop
  29 thread cancellation clean-up handlers while saving cancelability type
  30 .SH SYNOPSIS
  31 .nf
  32 .B #include <pthread.h>
  33 .PP
  34 .BI "void pthread_cleanup_push_defer_np(void (*" routine ")(void *),"
  35 .BI "                                   void *" arg );
  36 .BI "void pthread_cleanup_pop_restore_np(int " execute );
  37 .fi
  38 .PP
  39 Compile and link with \fI\-pthread\fP.
  40 .PP
  41 .in -4n
  42 Feature Test Macro Requirements for glibc (see
  43 .BR feature_test_macros (7)):
  44 .in
  45 .PP
  46 .ad l
  47 .BR pthread_cleanup_push_defer_np (),
  48 .BR pthread_cleanup_pop_defer_np ():
  49 .RS 4
  50 _GNU_SOURCE
  51 .RE
  52 .ad
  53 .SH DESCRIPTION
  54 These functions are the same as
  55 .BR pthread_cleanup_push (3)
  56 and
  57 .BR pthread_cleanup_pop (3),
  58 except for the differences noted on this page.
  59 .PP
  60 Like
  61 .BR pthread_cleanup_push (3),
  62 .BR pthread_cleanup_push_defer_np ()
  63 pushes
  64 .I routine
  65 onto the thread's stack of cancellation clean-up handlers.
  66 In addition, it also saves the thread's current cancelability type,
  67 and sets the cancelability type to "deferred" (see
  68 .BR pthread_setcanceltype (3));
  69 this ensures that cancellation clean-up will occur
  70 even if the thread's cancelability type was "asynchronous"
  71 before the call.
  72 .PP
  73 Like
  74 .BR pthread_cleanup_pop (3),
  75 .BR pthread_cleanup_pop_restore_np ()
  76 pops the top-most clean-up handler from the thread's
  77 stack of cancellation clean-up handlers.
  78 In addition, it restores the thread's cancelability
  79 type to its value at the time of the matching
  80 .BR pthread_cleanup_push_defer_np ().
  81 .PP
  82 The caller must ensure that calls to these
  83 functions are paired within the same function,
  84 and at the same lexical nesting level.
  85 Other restrictions apply, as described in
  86 .BR pthread_cleanup_push (3).
  87 .PP
  88 This sequence of calls:
  89 .PP
  90 .in +4n
  91 .EX
  92 pthread_cleanup_push_defer_np(routine, arg);
  93 pthread_cleanup_pop_restore_np(execute);
  94 .EE
  95 .in
  96 .PP
  97 is equivalent to (but shorter and more efficient than):
  98 .PP
  99 .\" As far as I can see, LinuxThreads reverses the two substeps
 100 .\" in the push and pop below.
 101 .in +4n
 102 .EX
 103 int oldtype;
 104
 105 pthread_cleanup_push(routine, arg);
 106 pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldtype);
 107 \&...
 108 pthread_setcanceltype(oldtype, NULL);
 109 pthread_cleanup_pop(execute);
 110 .EE
 111 .in
 112 .\" SH VERSIONS
 113 .\" Available since glibc 2.0
 114 .SH CONFORMING TO
 115 These functions are nonstandard GNU extensions;
 116 hence the suffix "_np" (nonportable) in the names.
 117 .SH SEE ALSO
 118 .BR pthread_cancel (3),
 119 .BR pthread_cleanup_push (3),
 120 .BR pthread_setcancelstate (3),
 121 .BR pthread_testcancel (3),
 122 .BR pthreads (7)