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/*
* waitpid.c --
*
* This procedure emulates the POSIX waitpid kernel call on
* BSD systems that don't have waitpid but do have wait3.
* This code is based on a prototype version written by
* Mark Diekhans and Karl Lehenbauer.
*
* Copyright (c) 1993 The Regents of the University of California.
* Copyright (c) 1994 Sun Microsystems, Inc.
*
* See the file "license.terms" for information on usage and redistribution
* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*
* RCS: @(#) $Id: waitpid.c,v 1.2 1998/09/14 18:39:45 stanton Exp $
*/
#include "tclInt.h"
#include "tclPort.h"
/*
* A linked list of the following structures is used to keep track
* of processes for which we received notification from the kernel,
* but the application hasn't waited for them yet (this can happen
* because wait may not return the process we really want). We
* save the information here until the application finally does
* wait for the process.
*/
typedef struct WaitInfo {
int pid; /* Pid of process that exited. */
WAIT_STATUS_TYPE status; /* Status returned when child exited
* or suspended. */
struct WaitInfo *nextPtr; /* Next in list of exited processes. */
} WaitInfo;
static WaitInfo *deadList = NULL; /* First in list of all dead
* processes. */
/*
*----------------------------------------------------------------------
*
* waitpid --
*
* This procedure emulates the functionality of the POSIX
* waitpid kernel call, using the BSD wait3 kernel call.
* Note: it doesn't emulate absolutely all of the waitpid
* functionality, in that it doesn't support pid's of 0
* or < -1.
*
* Results:
* -1 is returned if there is an error in the wait kernel call.
* Otherwise the pid of an exited or suspended process is
* returned and *statusPtr is set to the status value of the
* process.
*
* Side effects:
* None.
*
*----------------------------------------------------------------------
*/
#ifdef waitpid
# undef waitpid
#endif
int
waitpid(pid, statusPtr, options)
int pid; /* The pid to wait on. Must be -1 or
* greater than zero. */
int *statusPtr; /* Where to store wait status for the
* process. */
int options; /* OR'ed combination of WNOHANG and
* WUNTRACED. */
{
register WaitInfo *waitPtr, *prevPtr;
int result;
WAIT_STATUS_TYPE status;
if ((pid < -1) || (pid == 0)) {
errno = EINVAL;
return -1;
}
/*
* See if there's a suitable process that has already stopped or
* exited. If so, remove it from the list of exited processes and
* return its information.
*/
for (waitPtr = deadList, prevPtr = NULL; waitPtr != NULL;
prevPtr = waitPtr, waitPtr = waitPtr->nextPtr) {
if ((pid != waitPtr->pid) && (pid != -1)) {
continue;
}
if (!(options & WUNTRACED) && (WIFSTOPPED(waitPtr->status))) {
continue;
}
result = waitPtr->pid;
*statusPtr = *((int *) &waitPtr->status);
if (prevPtr == NULL) {
deadList = waitPtr->nextPtr;
} else {
prevPtr->nextPtr = waitPtr->nextPtr;
}
ckfree((char *) waitPtr);
return result;
}
/*
* Wait for any process to stop or exit. If it's an acceptable one
* then return it to the caller; otherwise store information about it
* in the list of exited processes and try again. On systems that
* have only wait but not wait3, there are several situations we can't
* handle, but we do the best we can (e.g. can still handle some
* combinations of options by invoking wait instead of wait3).
*/
while (1) {
#if NO_WAIT3
if (options & WNOHANG) {
return 0;
}
if (options != 0) {
errno = EINVAL;
return -1;
}
result = wait(&status);
#else
result = wait3(&status, options, 0);
#endif
if ((result == -1) && (errno == EINTR)) {
continue;
}
if (result <= 0) {
return result;
}
if ((pid != result) && (pid != -1)) {
goto saveInfo;
}
if (!(options & WUNTRACED) && (WIFSTOPPED(status))) {
goto saveInfo;
}
*statusPtr = *((int *) &status);
return result;
/*
* Can't return this info to caller. Save it in the list of
* stopped or exited processes. Tricky point: first check for
* an existing entry for the process and overwrite it if it
* exists (e.g. a previously stopped process might now be dead).
*/
saveInfo:
for (waitPtr = deadList; waitPtr != NULL; waitPtr = waitPtr->nextPtr) {
if (waitPtr->pid == result) {
waitPtr->status = status;
goto waitAgain;
}
}
waitPtr = (WaitInfo *) ckalloc(sizeof(WaitInfo));
waitPtr->pid = result;
waitPtr->status = status;
waitPtr->nextPtr = deadList;
deadList = waitPtr;
waitAgain: continue;
}
}
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