diff options
author | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2013-01-13 18:53:00 +0000 |
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committer | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2013-01-13 18:53:00 +0000 |
commit | b3f3dd123c181fe851f0a9756bed7acd4ba4ef7d (patch) | |
tree | df530299e0171e8a86a2709ed4f19a1468efda4e /nuttx/sched/sched_waitpid.c | |
parent | ffda55b34a9a8a4a84f4cbc1da3836b944baec46 (diff) | |
download | px4-firmware-b3f3dd123c181fe851f0a9756bed7acd4ba4ef7d.tar.gz px4-firmware-b3f3dd123c181fe851f0a9756bed7acd4ba4ef7d.tar.bz2 px4-firmware-b3f3dd123c181fe851f0a9756bed7acd4ba4ef7d.zip |
Use SIGCHLD with waitpid(); implemented wait() and waitid()
git-svn-id: http://svn.code.sf.net/p/nuttx/code/trunk@5515 42af7a65-404d-4744-a932-0658087f49c3
Diffstat (limited to 'nuttx/sched/sched_waitpid.c')
-rw-r--r-- | nuttx/sched/sched_waitpid.c | 192 |
1 files changed, 176 insertions, 16 deletions
diff --git a/nuttx/sched/sched_waitpid.c b/nuttx/sched/sched_waitpid.c index 692ef6410..dc715b2e9 100644 --- a/nuttx/sched/sched_waitpid.c +++ b/nuttx/sched/sched_waitpid.c @@ -1,7 +1,7 @@ /***************************************************************************** * sched/sched_waitpid.c * - * Copyright (C) 2011-2012 Gregory Nutt. All rights reserved. + * Copyright (C) 2011-2013 Gregory Nutt. All rights reserved. * Author: Gregory Nutt <gnutt@nuttx.org> * * Redistribution and use in source and binary forms, with or without @@ -41,13 +41,14 @@ #include <sys/wait.h> #include <semaphore.h> +#include <signal.h> #include <errno.h> #include <nuttx/sched.h> #include "os_internal.h" -#ifdef CONFIG_SCHED_WAITPID /* Experimental */ +#ifdef CONFIG_SCHED_WAITPID /***************************************************************************** * Private Functions @@ -58,7 +59,7 @@ *****************************************************************************/ /***************************************************************************** - * Name: sched_waitpid + * Name: waitpid * * Description: * @@ -172,10 +173,16 @@ * *****************************************************************************/ -/***************************************************************************/ -/* NOTE: This is a partially functional, experimental version of waitpid() */ -/***************************************************************************/ +/*************************************************************************** + * NOTE: This is a partially functional, experimental version of waitpid() + * + * If there is no SIGCHLD signal supported (CONFIG_SCHED_HAVE_PARENT not + * defined), then waitpid() is still available, but does not obey the + * restriction that the pid be a child of the caller. + * + ***************************************************************************/ +#ifndef CONFIG_SCHED_HAVE_PARENT pid_t waitpid(pid_t pid, int *stat_loc, int options) { _TCB *tcb; @@ -183,9 +190,24 @@ pid_t waitpid(pid_t pid, int *stat_loc, int options) int err; int ret; + DEBUGASSERT(stat_loc); + + /* None of the options are supported */ + +#ifdef CONFIG_DEBUG + if (options != 0) + { + set_errno(ENOSYS); + return ERROR; + } +#endif + /* Disable pre-emption so that nothing changes in the following tests */ sched_lock(); + + /* Get the TCB corresponding to this PID */ + tcb = sched_gettcb(pid); if (!tcb) { @@ -193,16 +215,6 @@ pid_t waitpid(pid_t pid, int *stat_loc, int options) goto errout_with_errno; } - /* None of the options are supported */ - -#ifdef CONFIG_DEBUG - if (options != 0) - { - err = ENOSYS; - goto errout_with_errno; - } -#endif - /* "If more than one thread is suspended in waitpid() awaiting termination of * the same process, exactly one thread will return the process status at the * time of the target process termination." Hmmm.. what do we return to the @@ -245,4 +257,152 @@ errout: return ERROR; } +/*************************************************************************** + * + * If CONFIG_SCHED_HAVE_PARENT is defined, then waitpid will use the SIGHCLD + * signal. It can also handle the pid == (pid_t)-1 arguement. This is + * slightly more spec-compliant. + * + * But then I have to be concerned about the fact that NuttX does not queue + * signals. This means that a flurry of signals can cause signals to be + * lost (or to have the data in the struct siginfo to be overwritten by + * the next signal). + * + ***************************************************************************/ + +#else +pid_t waitpid(pid_t pid, int *stat_loc, int options) +{ + FAR _TCB *rtcb = (FAR _TCB *)g_readytorun.head; + FAR struct siginfo info; + sigset_t sigset; + int err; + int ret; + + DEBUGASSERT(stat_loc); + + /* None of the options are supported */ + +#ifdef CONFIG_DEBUG + if (options != 0) + { + set_errno(ENOSYS); + return ERROR; + } +#endif + + /* Create a signal set that contains only SIGCHLD */ + + (void)sigemptyset(&sigset); + (void)sigaddset(&sigset, SIGCHLD); + + /* Disable pre-emption so that nothing changes while the loop executes */ + + sched_lock(); + + /* Verify that this task actually has children and that the the requeste + * TCB is actually a child of this task. + */ + + if (rtcb->nchildren == 0) + { + err = ECHILD; + goto errout_with_errno; + } + else if (pid != (pid_t)-1) + { + /* Get the TCB corresponding to this PID and make sure it is our child. */ + + FAR _TCB *ctcb = sched_gettcb(pid); + if (!ctcb || ctcb->parent != rtcb->pid) + { + err = ECHILD; + goto errout_with_errno; + } + } + + /* Loop until the child that we are waiting for dies */ + + for (;;) + { + /* Check if the task has already died. Signals are not queued in + * NuttX. So a possibility is that the child has died and we + * missed the death of child signal (we got some other signal + * instead). + */ + + if (pid == (pid_t)-1) + { + /* We are waiting for any child, check if there are still + * chilren. + */ + + if (rtcb->nchildren == 0) + { + /* There were one or more children when we started so they + * must have exit'ed. There are just no bread crumbs left + * behind to tell us the PID(s) of the existed children. + * Reporting ECHLD is about all we can do in this case. + */ + + err = ECHILD; + goto errout_with_errno; + } + } + else + { + /* We are waiting for a specific PID. We can use kill() with + * signal number 0 to determine if that task is still alive. + */ + + ret = kill(pid, 0); + if (ret < 0) + { + /* It is no longer running. We know that the child task was + * running okay when we started, so we must have lost the + * signal. In this case, we know that the task exit'ed, but + * we do not know its exit status. It would be better to + * reported ECHILD that bogus status. + */ + + err = ECHILD; + goto errout_with_errno; + } + } + + /* Wait for any death-of-child signal */ + + ret = sigwaitinfo(&sigset, &info); + if (ret < 0) + { + goto errout_with_lock; + } + + /* Was this the death of the thread we were waiting for? In the of + * pid == (pid_t)-1, we are waiting for any child thread. + */ + + if (info.si_signo == SIGCHLD && + (pid == (pid_t)-1 || info.si_pid == pid)) + { + /* Yes... return the status and PID (in the event it was -1) */ + + *stat_loc = info.si_status; + pid = info.si_pid; + break; + } + } + + sched_unlock(); + return (int)pid; + +errout_with_errno: + set_errno(err); + +errout_with_lock: + sched_unlock(); + return ERROR; +} +#endif /* CONFIG_SCHED_HAVE_PARENT */ + #endif /* CONFIG_SCHED_WAITPID */ |