X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;ds=inline;f=kern%2Fsignal.c;h=0243987be76ac237b4b0c9ce8704b294f9584498;hb=0168eb0bee0da568cd3ea8f8dfffa9343175efd9;hp=62cfd74c1a9425d3c861a7bd290174817f0f8576;hpb=a8ed288597f0fac2f01347a80ed781964d09b663;p=bertos.git diff --git a/kern/signal.c b/kern/signal.c index 62cfd74c..0243987b 100755 --- a/kern/signal.c +++ b/kern/signal.c @@ -2,43 +2,103 @@ * \file * * * \brief IPC signals implementation. * - * Each process can wait for just one signal. - * Multiple processes can wait for the same signal. In this - * case, each signal will wake-up one of them. + * Signals are a low-level IPC primitive. A process receives a signal + * when some external event has happened. Like interrupt requests, + * signals do not carry any additional information. If processing a + * specific event requires additional data, the process must obtain it + * through some other mechanism. * - * \version $Id$ + * Despite the name, one shouldn't confuse these signals with POSIX + * signals. POSIX signals are usually executed synchronously, like + * software interrupts. * - * \author Bernardo Innocenti - */ - -/* - * $Log$ - * Revision 1.4 2004/07/30 14:30:27 rasky - * Resa la sig_signal interrupt safe (con il nuovo scheduler IRQ-safe) - * Rimossa event_doIntr (ora inutile) e semplificata la logica delle macro con funzioni inline + * In this implementation, each process has a limited set of signal + * bits (usually 32) and can wait for multiple signals at the same + * time using sig_wait(). Signals can also be polled using sig_check(), + * but a process spinning on its signals usually defeats their purpose + * of providing a multitasking-friendly infrastructure for event-driven + * applications. + * + * Signals are like flags: they are either active or inactive. After an + * external event has delivered a particular signal, it remains raised until + * the process acknowledges it using either sig_wait() or sig_check(). + * Counting signals is not a reliable way to count how many times a + * particular event has occurred, because the same signal may be + * delivered twice before the process can notice. + * + * Any execution context, including an interrupt handler, can deliver + * a signal to a process using sig_signal(). Multiple distinct signals + * may be delivered at once with a single invocation of sig_signal(), + * although this is rarely useful. + * + * There's no hardcoded mapping of specific events to signal bits. + * The meaning of a particular signal bit is defined by an agreement + * between the delivering entity and the receiving process. + * For instance, a terminal driver may be written to deliver + * a signal bit called SIG_INT when it reads the CTRL-C sequence + * from the keyboard, and a process may react to it by quitting. * - * Revision 1.3 2004/07/30 14:24:16 rasky - * Task switching con salvataggio perfetto stato di interrupt (SR) - * Kernel monitor per dump informazioni su stack dei processi + * The SIG_SINGLE bit is reserved for a special purpose (this is + * more a suggestion than a constraint). When a process wants + * wait for a single event on the fly, it needs not allocate a + * free signal from its pool. Instead, SIG_SINGLE can be used * - * Revision 1.2 2004/06/03 11:27:09 bernie - * Add dual-license information. + * The "event" module is a higher-level interface that can optionally + * deliver signals to processes. Messages provide even higher-level + * IPC services built on signals. Semaphore arbitration is also + * implemented using signals. * - * Revision 1.1 2004/05/23 17:27:00 bernie - * Import kern/ subdirectory. + * Signals are very low overhead. Using them exclusively to wait + * for multiple asynchronous events results in very simple dispatch + * logic with low processor and resource usage. * + * + * \version $Id$ + * + * \author Bernardo Innocenti */ +/*#* + *#* $Log$ + *#* Revision 1.8 2004/09/14 21:06:44 bernie + *#* Use debug.h instead of kdebug.h. + *#* + *#* Revision 1.7 2004/08/25 14:12:09 rasky + *#* Aggiornato il comment block dei log RCS + *#* + *#* Revision 1.6 2004/08/14 19:37:57 rasky + *#* Merge da SC: macros.h, pool.h, BIT_CHANGE, nome dei processi, etc. + *#* + *#* Revision 1.5 2004/08/04 21:50:33 bernie + *#* Add extensive documentation. + *#* + *#* Revision 1.4 2004/07/30 14:30:27 rasky + *#* Resa la sig_signal interrupt safe (con il nuovo scheduler IRQ-safe) + *#* Rimossa event_doIntr (ora inutile) e semplificata la logica delle macro con funzioni inline + *#* + *#* Revision 1.3 2004/07/30 14:24:16 rasky + *#* Task switching con salvataggio perfetto stato di interrupt (SR) + *#* Kernel monitor per dump informazioni su stack dei processi + *#* + *#* Revision 1.2 2004/06/03 11:27:09 bernie + *#* Add dual-license information. + *#* + *#* Revision 1.1 2004/05/23 17:27:00 bernie + *#* Import kern/ subdirectory. + *#* + *#*/ + #include "signal.h" #include "proc.h" #include "proc_p.h" #include "hw.h" +#include // FIXME #if CONFIG_KERN_SIGNALS @@ -77,6 +137,10 @@ sigset_t sig_wait(sigset_t sigs) /* go to sleep and proc_schedule() another process */ CurrentProcess->sig_wait = sigs; proc_schedule(); + + /* When we come back here, a signal must be arrived */ + ASSERT(!CurrentProcess->sig_wait); + ASSERT(CurrentProcess->sig_recv); } /* Signals found: clear them and return */