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lam_kpause

NAME

lam_ksigblock, lam_ksigsetmask, lam_ksigretry, lam_ksigsetretry, lam_kpause - Manipulate LAM signal handling policy.

SYNOPSIS

 #include <lam_ksignal.h>
 
 int lam_ksigblock (int mask);
 int lam_ksigsetmask (int mask);
 int lam_ksigretry (int mask);
 int lam_ksigsetretry (int mask);
 int lam_kpause ();
 
 int lam_ksigmask (int signum);
 

DESCRIPTION

As part of the signal handling package, LAM maintains two system masks, a block mask and a retry mask. Each contains a bit for every defined signal. The block mask will prevent a signal from being handled if its corresponding bit is set. The retry mask indicates whether a system call to the daemon should be retried after an given signal is handled. Signals are defined in <lam_ksignal.h> and described in lam_ksignal(2).

lam_ksigblock() sets the block mask to block each signal whose corresponding bit in the mask argument is set, as well as those whose bits were set in the original block mask. lam_ksigsetmask() explictly sets the system block mask to the mask argument. All signals set in the mask argument become blocked - all others become unblocked. Both routines return the previous value of the block mask.

All signals begin as unblocked, and privileged signals cannot be blocked. A blocked signal is not ignored - it is impeded. If the block should be removed for a signal that was pending, the signal handler will immediately be called. Several impeded signals will fuse together as one and not be handled distinctly.

Since some LAM daemon functions cause the calling process to block there is an excellent chance that a system call will be interrupted by a signal. When this happens, the blocking function returns with the error EINTR. If the bit corresponding to the delivered signal is set in the retry mask, the daemon request will be automatically retried after the signal handler returns.

lam_ksigretry() resets the retry mask to retry each signal whose corresponding bit in the mask argument is set, as well as those whose bits were set in the original retry mask. lam_ksigsetmask() explictly sets the system retry mask to the mask argument. All signals set in the mask argument will be retried - all others will not be retried. Both routines return the previous value of the retry mask. Initially, all signals will be retried except SIGRELEASE, which cannot be retried.

The macro lam_ksigmask(signum), defined in <lam_ksignal.h>, converts a signal number into a mask with only the corresponding bit set.

lam_kpause() causes the calling process to wait until any signal is delivered.

RETURN VALUE

lam_ksigblock(), lam_ksigsetmask(), lam_ksigretry() and lam_ksigsetretry() all return the previous mask value. lam_kpause() always returns -1 and the global variable errno is always set to EINTR.

SEE ALSO

lam_ksignal(2), MPIL_Signal(2)