--- name: "lam_ksignal" section: "2" platform: "linux" package: "lam2-dev" version: "6.3.2-3" release: "Debian 2.2 (Potato)" platforms: ["linux"] url: "https://new.carta.tech/lam_ksignal" --- # lam\_ksignal(2) Specify a signal handler for a LAM signal. ## NAME lam\_ksignal - Specify a signal handler for a LAM signal. ## SYNOPSIS \#include \ void (\*lam\_ksignal (int signum, void (\*func)())) (); ## DESCRIPTION *lam\_ksignal()* exchanges a current signal handler for a new signal handler. When a process is signalled, execution control passes immediately to the handler function. Control passes back to the previous location when the handler function returns. Each signal begins with a default handler when the process is initialized. LAM signals are completely separate from the signal facilities of the host operating system. While the syntax and functionality are similar, [signal(3)](/signal/3.md) cannot affect LAM signals and vice versa. The following is a list of LAM signals as they appear in \. ``` LAM_SIGTRACE 1 unload trace data LAM_SIGUDIE 4 terminate LAM_SIGARREST 5 suspend execution LAM_SIGRELEASE 6 continue execution LAM_SIGA 7 user defined LAM_SIGB 8 user defined LAM_SIGFUSE 9 node about to die LAM_SIGSHRINK 10 another node has died ``` By default, LAM\_SIGA and LAM\_SIGB are ignored. They are reserved for application programmers LAM\_SIGUDIE causes the signalled process to exit. LAM\_SIGARREST causes the signalled process to indefinitely block and LAM\_SIGRELEASE reschedules it. LAM\_SIGTRACE causes the current contents of the trace buffer to be flushed to the local trace daemon. LAM\_SIGFUSE and LAM\_SIGSHRINK are fault tolerant signals. The former indicates that the local node and all its processes will terminate imminently. The process receiving LAM\_SIGFUSE should take immediate action to clean up. By default, LAM\_SIGFUSE is ignored. LAM\_SIGSHRINK indicates that another node has died or been forcefully terminated. The default action is to flush the route cache so that subsequent remote service calls to the dead node will fail with EBADNODE (in \). If the application decides to trap this signal, the signal handler should call the old handler (the default which will be returned by *lam\_ksignal()*) before returning. The new signal handler must be the address of a function. The special value LAM\_KSIG\_IGN ignores the given signal. (A function that does nothing is called when the signal occurs.) Another special value, LAM\_KSIG\_DFL, returns the signal handler to the default function. When a signal handler is called, the signal number that caused the invocation is passed as the sole parameter to the handler. While an signal handler is running, further signals on the same number are blocked. Interrupts do not form queues. A second signal will overwrite the first (thus two appear as one) if the first has not yet been handled, either due to scheduling or signal blocking. ## RETURN VALUE Upon successful completion, the address of the previously installed signal handler, which may be reinstated later, is returned. Otherwise, -1 is returned and the global variable *errno* is set to indicate the error. ## ERRORS - EINVAL The signal number is invalid or privileged. ## SEE ALSO [MPIL\_Signal(2)](/MPIL_Signal/2.md), [lam\_ksigblock(2)](/lam_ksigblock/2.md)