X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=kern%2Fsignal.c;h=6194251702a0d4eb3dabb1c67ee5e7d434708b8a;hb=d79f7d6dbc485204f897c9a5ea1f26936cc23744;hp=5c62e50a69008177a7aa29d9651b6323574cebf6;hpb=96f0ef786b54356c56cc3d4e4f0838df2505cfcc;p=bertos.git diff --git a/kern/signal.c b/kern/signal.c old mode 100755 new mode 100644 index 5c62e50a..61942517 --- a/kern/signal.c +++ b/kern/signal.c @@ -1,114 +1,192 @@ -/*! +/** * \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 1.2 2004/06/03 11:27:09 bernie - * Add dual-license information. + * 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. * - * Revision 1.1 2004/05/23 17:27:00 bernie - * Import kern/ subdirectory. + * 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. + * + * 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 + * + * 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. + * + * 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 */ #include "signal.h" -#include "proc.h" -#include "proc_p.h" -#include "hw.h" -// FIXME +#include +#include +#include +#include + + #if CONFIG_KERN_SIGNALS -/*! +/** * Check if any of the signals in \a sigs has occurred and clear them. - * Return the signals that have occurred. + * \return the signals that have occurred. */ -sigset_t sig_check(sigset_t sigs) +sigmask_t sig_check(sigmask_t sigs) { - sigset_t result; + sigmask_t result; + cpuflags_t flags; - DISABLE_INTS; + IRQ_SAVE_DISABLE(flags); result = CurrentProcess->sig_recv & sigs; CurrentProcess->sig_recv &= ~sigs; - ENABLE_INTS; + IRQ_RESTORE(flags); + return result; } -/*! +/** * Sleep until any of the signals in \a sigs occurs. - * Return the signal(s) that have awaked the process. + * \return the signal(s) that have awaked the process. */ -sigset_t sig_wait(sigset_t sigs) +sigmask_t sig_wait(sigmask_t sigs) { - sigset_t result; + sigmask_t result; + cpuflags_t flags; - DISABLE_INTS; + IRQ_SAVE_DISABLE(flags); - for(;;) + /* Loop until we get at least one of the signals */ + while (!(result = CurrentProcess->sig_recv & sigs)) { - /* Check if we got at least one of the signals */ - if ((result = CurrentProcess->sig_recv & sigs)) - { - /* Yes, clear signals and return */ - CurrentProcess->sig_recv &= ~sigs; - ENABLE_INTS; - return result; - } - - /* No, go to sleep and proc_schedule() another process */ + /* 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 */ + CurrentProcess->sig_recv &= ~sigs; -/*! - * Send the signals \a sigs to the process \a proc. - * The process will be awaken if it was waiting for any of them. - * - * This call is interrupt safe (no \c DISABLE_INTS/ENABLE_INTS protection) + IRQ_RESTORE(flags); + return result; +} + +/** + * Sleep until any of the signals in \a sigs or \a timeout ticks elapse. + * If the timeout elapse a SIG_TIMEOUT is added to the received signal(s). + * \return the signal(s) that have awaked the process. + * \note Caller must check return value to check which signal has awaked the process. */ -void _sig_signal(Process *proc, sigset_t sigs) +sigmask_t sig_waitTimeout(sigmask_t sigs, ticks_t timeout) { - /* Set the signals */ - proc->sig_recv |= sigs; - - /* Check if process needs to be awaken */ - if (proc->sig_recv & proc->sig_wait) - { - /* Wake up process and enqueue in ready list */ - proc->sig_wait = 0; - SCHED_ENQUEUE(proc); - } + Timer t; + sigmask_t res; + cpuflags_t flags; + + ASSERT(!sig_check(SIG_TIMEOUT)); + ASSERT(!(sigs & SIG_TIMEOUT)); + /* IRQ are needed to run timer */ + ASSERT(IRQ_ENABLED); + + timer_set_event_signal(&t, proc_current(), SIG_TIMEOUT); + timer_setDelay(&t, timeout); + timer_add(&t); + res = sig_wait(SIG_TIMEOUT | sigs); + + IRQ_SAVE_DISABLE(flags); + /* Remove timer if sigs occur before timer signal */ + if (!(res & SIG_TIMEOUT) && !sig_check(SIG_TIMEOUT)) + timer_abort(&t); + IRQ_RESTORE(flags); } -/*! - * Same as _sig_signal() with interrupt protection. +/** + * Send the signals \a sigs to the process \a proc. + * The process will be awaken if it was waiting for any of them. * - * \note Inlined manually because some compilers are too - * stupid to it automatically. + * \note This call is interrupt safe. */ -void sig_signal(Process *proc, sigset_t sigs) +void sig_signal(Process *proc, sigmask_t sigs) { - DISABLE_INTS; + cpuflags_t flags; + IRQ_SAVE_DISABLE(flags); /* Set the signals */ proc->sig_recv |= sigs; @@ -121,7 +199,7 @@ void sig_signal(Process *proc, sigset_t sigs) SCHED_ENQUEUE(proc); } - ENABLE_INTS; + IRQ_RESTORE(flags); } #endif /* CONFIG_KERN_SIGNALS */