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ecbsuspend |
Portability: | SAS/C extension |
SYNOPSIS | |
DESCRIPTION | |
RETURN VALUE | |
CAUTIONS | |
IMPLEMENTATION | |
EXAMPLE | |
RELATED FUNCTIONS | |
SEE ALSO |
SYNOPSIS |
#include <lcsignal.h> int ecbsuspend(sigset_t *mask, size_t listsize, struct _ecblist *ecblist);
DESCRIPTION |
ecbsuspend
delays program execution until it receives a C signal or until an
Event Control Block (ECB) is posted.
mask
specifies the set of signals to be blocked while execution is delayed.
listsize
specifies the number of
_ecblist
structures addressed by the
ecblist
argument.
ecblist
is the address
of an array of structures, each of which represents one or more contiguous
ECBs. Each structure contains two members: a count of the number of ECBs
and the address of an array of ECBs. The count may be zero, in which case
the ECB array address is ignored.
The declaration for the
_ecblist
structure is
struct _ecblist { size_t count; unsigned *ecbarr; }
The ECB list for
ecbsuspend
is passed by the
_ecblist
structure
for several reasons. It enables a static ECB list to be used in many cases
because individual ECBs can easily be removed by setting their
count
member to 0. For applications that have a large number of ECBs,
the
_ecblist
structure facilitates organizing
them into arrays; this method may slightly improve the performance of
ecbsuspend
because fewer memory accesses are
required to determine the addresses of all the ECBs.
ecbsuspend
returns
to its caller when one of the following events occurs:
ecbsuspend
.
Several conditions for completion of the
ecbsuspend
function may
occur simultaneously or nearly simultaneously.
In such cases, a signal handler may be called even though an ECB was POSTed
before or during arrival of the signal. On return from
ecbsuspend
, any number of ECBs may be POSTed, and more than one signal
handler may have been called if the signal mask permits it.
RETURN VALUE |
ecbsuspend
returns -1 if it was terminated due to receipt of a signal or
due to an error. (
errno
is set to
EINTR
if the cause was a signal.)
ecbsuspend
returns 0 if it returned because an ECB was posted.
CAUTIONS |
ecbsuspend
does not clear any ECBs addressed by the
ecblist
argument. It is the caller's responsibility to clear the ECBs
after a POST and to initialize them to zero or to some other suitable value.
The value returned by
ecbsuspend
may not be completely reliable. An ECB may have been POSTed even though
a signal was detected, and a signal may have been received after
ecbsuspend
was awakened by a POST but before return to the user program
was completely effected.
IMPLEMENTATION |
ecbsuspend
builds a standard OS ECB list for the ECBs indicated by its arguments,
in addition to an ECB used internally by signal handling, and issues the OS
WAIT macro to wait for a single ECB to be POSTed. If USS is active, the USS
mvspause
system call is used in place of an OS
WAIT.
EXAMPLE |
Wait for an alarm signal or for a POST representing a reply from the OS/390 operator:
#include <lcsignal.h> #include <ctype.h> /* flag for SIGALRM handle */ static int toolate = 0; static void timesup(int signum); int confirm() { unsigned ECB = 0; struct _ecblist myECBs = {1, 0 } ; char reply; sigset_t nosigs; /* Set up ECB list for single ECB. */ myECBs.ecbarr = &ECB; /* Issue WTOR macro via assembler. */ /* subroutine (not shown) */ wtor("Reply U to confirm request.", &reply, &ECB); /*Catch SIGALRM signal. */ signal(SIGALRM, ×up); /* Wait 2 minutes for reply. */ toolate = 0; alarm(120); /* Set no sigs blocked for suspend. */ sigemptyset(&nosigs); ecbsuspend(&nosigs, 1, &myECBs); /* Cancel alarm. */ alarm(0); /* Restore default alarm handling. */ signal(SIGALRM, SIG_DFL); /* If the ECB was posted, */ /* return whether OK given. */ if (ECB & 0x40000000) return toupper(reply) == 'U'; /* If we ran out of time, */ /* call asm to delete reply. */ else if(toolate){ dom(); /* Tell caller not to do it. */ puts("No reply received, treated as permission denied. "); return 0; } } static void timesup(int signum) { toolate = 1; return; }
RELATED FUNCTIONS |
ecbpause
,
sigpause
,
sigsuspend
SEE ALSO |
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