X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;ds=sidebyside;f=src%2Fruntime%2Finterrupt.c;h=24538f93308d706dd22beb5ec7305b3c6a00006d;hb=6fb6e66f531dfb6140ec3e0cc8f84f6ecd1927ca;hp=94b2de85dac4fd03f2148c25b0124c346a7f4bbf;hpb=e8c27392f426b5ebe180fa07b220a9b650a49061;p=sbcl.git diff --git a/src/runtime/interrupt.c b/src/runtime/interrupt.c index 94b2de8..24538f9 100644 --- a/src/runtime/interrupt.c +++ b/src/runtime/interrupt.c @@ -14,6 +14,7 @@ */ #include +#include #include #ifdef mach /* KLUDGE: #ifdef on lowercase symbols? Ick. -- WHN 19990904 */ @@ -73,17 +74,25 @@ os_context_t *lisp_interrupt_contexts[MAX_INTERRUPTS]; * In that case, the Lisp-level handler is stored in interrupt_handlers[..] * and interrupt_low_level_handlers[..] is cleared. * - * However, some signals need special handling, e.g. the SIGSEGV (for - * Linux) or SIGBUS (for FreeBSD) used by the garbage collector to - * detect violations of write protection, because some cases of such - * signals (e.g. GC-related violations of write protection) are - * handled at C level and never passed on to Lisp. For such signals, - * we still store any Lisp-level handler in interrupt_handlers[..], - * but for the outermost handle we use the value from - * interrupt_low_level_handlers[..], instead of the ordinary - * interrupt_handle_now(..) or interrupt_handle_later(..). + * However, some signals need special handling, e.g. * - * -- WHN 20000728 */ + * o the SIGSEGV (for e.g. Linux) or SIGBUS (for e.g. FreeBSD) used by the + * garbage collector to detect violations of write protection, + * because some cases of such signals (e.g. GC-related violations of + * write protection) are handled at C level and never passed on to + * Lisp. For such signals, we still store any Lisp-level handler + * in interrupt_handlers[..], but for the outermost handle we use + * the value from interrupt_low_level_handlers[..], instead of the + * ordinary interrupt_handle_now(..) or interrupt_handle_later(..). + * + * o the SIGTRAP (Linux/Alpha) which Lisp code uses to handle breakpoints, + * pseudo-atomic sections, and some classes of error (e.g. "function + * not defined"). This never goes anywhere near the Lisp handlers at all. + * See runtime/alpha-arch.c and code/signal.lisp + * + * - WHN 20000728, dan 20010128 */ + + void (*interrupt_low_level_handlers[NSIG]) (int, siginfo_t*, void*) = {0}; union interrupt_handler interrupt_handlers[NSIG]; @@ -131,8 +140,8 @@ fake_foreign_function_call(os_context_t *context) == current_control_frame_pointer) { /* There is a small window during call where the callee's * frame isn't built yet. */ - if (LowtagOf(*os_context_register_addr(context, reg_CODE)) - == type_FunctionPointer) { + if (lowtagof(*os_context_register_addr(context, reg_CODE)) + == FUN_POINTER_LOWTAG) { /* We have called, but not built the new frame, so * build it for them. */ current_control_frame_pointer[0] = @@ -205,6 +214,7 @@ undo_fake_foreign_function_call(os_context_t *context) * FREE_INTERRUPT_CONTEXT_INDEX? If so, we should say so. And * perhaps yes, unbind_to_here() really would be clearer and less * fragile.. */ + /* dan (2001.08.10) thinks the above supposition is probably correct */ unbind(); #ifdef reg_ALLOC @@ -254,6 +264,13 @@ interrupt_internal_error(int signal, siginfo_t *info, os_context_t *context, } } +/* This function handles pending interrupts. Note that in C/kernel + * terms we dealt with the signal already; we just haven't decided + * whether to call a Lisp handler or do a GC or something like that. + * If it helps, you can think of pending_{signal,mask,info} as a + * one-element queue of signals that we have acknowledged but not + * processed */ + void interrupt_handle_pending(os_context_t *context) { @@ -280,9 +297,30 @@ interrupt_handle_pending(os_context_t *context) } } - /* FIXME: How come we unconditionally copy from pending_mask into - * the context, and then test whether pending_signal is set? If - * pending_signal wasn't set, how could pending_mask be valid? */ + /* FIXME: This isn't very clear. It would be good to reverse + * engineer it and rewrite the code more clearly, or write a clear + * explanation of what's going on in the comments, or both. + * + * WHN's question 1a: How come we unconditionally copy from + * pending_mask into the context, and then test whether + * pending_signal is set? + * + * WHN's question 1b: If pending_signal wasn't set, how could + * pending_mask be valid? + * + * Dan Barlow's reply (sbcl-devel 2001-03-13): And the answer is - + * or appears to be - because interrupt_maybe_gc set it that way + * (look in the #ifndef __i386__ bit). We can't GC during a + * pseudo-atomic, so we set maybe_gc_pending=1 and + * arch_set_pseudo_atomic_interrupted(..) When we come out of + * pseudo_atomic we're marked as interrupted, so we call + * interrupt_handle_pending, which does the GC using the pending + * context (it needs a context so that it has registers to use as + * GC roots) then notices there's no actual interrupt handler to + * call, so doesn't. That's the second question [1b] answered, + * anyway. Why we still need to copy the pending_mask into the + * context given that we're now done with the context anyway, I + * couldn't say. */ memcpy(os_context_sigmask_addr(context), &pending_mask, sizeof(sigset_t)); sigemptyset(&pending_mask); if (pending_signal) { @@ -341,7 +379,9 @@ interrupt_handle_now(int signal, siginfo_t *info, void *void_context) } #ifdef QSHOW_SIGNALS - FSHOW((stderr, "in interrupt_handle_now(%d, info, context)\n", signal)); + FSHOW((stderr, + "/entering interrupt_handle_now(%d, info, context)\n", + signal)); #endif if (ARE_SAME_HANDLER(handler.c, SIG_DFL)) { @@ -351,15 +391,14 @@ interrupt_handle_now(int signal, siginfo_t *info, void *void_context) * support decides to pass on it. */ lose("no handler for signal %d in interrupt_handle_now(..)", signal); - } else if (LowtagOf(handler.lisp) == type_FunctionPointer) { + } else if (lowtagof(handler.lisp) == FUN_POINTER_LOWTAG) { /* Allocate the SAPs while the interrupts are still disabled. * (FIXME: Why? This is the way it was done in CMU CL, and it * even had the comment noting that this is the way it was * done, but no motivation..) */ - lispobj context_sap = alloc_sap(context); - lispobj info_sap = alloc_sap(info); - + lispobj info_sap,context_sap = alloc_sap(context); + info_sap = alloc_sap(info); /* Allow signals again. */ sigprocmask(SIG_SETMASK, os_context_sigmask_addr(context), 0); @@ -389,6 +428,12 @@ interrupt_handle_now(int signal, siginfo_t *info, void *void_context) { undo_fake_foreign_function_call(context); } + +#ifdef QSHOW_SIGNALS + FSHOW((stderr, + "/returning from interrupt_handle_now(%d, info, context)\n", + signal)); +#endif } static void @@ -407,6 +452,9 @@ maybe_now_maybe_later(int signal, siginfo_t *info, void *void_context) * SET_FPU_CONTROL_WORD(context->__fpregs_mem.cw); * #endif */ + /* see comments at top of code/signal.lisp for what's going on here + * with INTERRUPTS_ENABLED/INTERRUPT_HANDLE_NOW + */ if (SymbolValue(INTERRUPTS_ENABLED) == NIL) { /* FIXME: This code is exactly the same as the code in the @@ -418,7 +466,6 @@ maybe_now_maybe_later(int signal, siginfo_t *info, void *void_context) os_context_sigmask_addr(context), sizeof(sigset_t)); sigaddset_blockable(os_context_sigmask_addr(context)); - SetSymbolValue(INTERRUPT_PENDING, T); } else if ( @@ -462,15 +509,21 @@ gc_trigger_hit(int signal, siginfo_t *info, os_context_t *context) context); return (badaddr >= current_auto_gc_trigger && - badaddr < DYNAMIC_SPACE_START + DYNAMIC_SPACE_SIZE); + badaddr < current_dynamic_space + DYNAMIC_SPACE_SIZE); } } #endif #ifndef __i386__ +/* This function gets called from the SIGSEGV (for e.g. Linux or + * OpenBSD) or SIGBUS (for e.g. FreeBSD) handler. Here we check + * whether the signal was due to treading on the mprotect()ed zone - + * and if so, arrange for a GC to happen. */ boolean -interrupt_maybe_gc(int signal, siginfo_t *info, os_context_t *context) +interrupt_maybe_gc(int signal, siginfo_t *info, void *void_context) { + os_context_t *context=(os_context_t *) void_context; + if (!foreign_function_call_active #ifndef INTERNAL_GC_TRIGGER && gc_trigger_hit(signal, info, context) @@ -481,6 +534,10 @@ interrupt_maybe_gc(int signal, siginfo_t *info, os_context_t *context) #endif if (arch_pseudo_atomic_atomic(context)) { + /* don't GC during an atomic operation. Instead, copy the + * signal mask somewhere safe. interrupt_handle_pending + * will detect pending_signal==0 and know to do a GC with the + * signal context instead of calling a Lisp-level handler */ maybe_gc_pending = 1; if (pending_signal == 0) { /* FIXME: This copy-pending_mask-then-sigaddset_blockable @@ -510,22 +567,78 @@ interrupt_maybe_gc(int signal, siginfo_t *info, os_context_t *context) * noise to install handlers */ -/* Install a special low-level handler for signal; or if handler is - * SIG_DFL, remove any special handling for signal. */ +/* + * what low-level signal handlers looked like before + * undoably_install_low_level_interrupt_handler() got involved + */ +struct low_level_signal_handler_state { + int was_modified; + void (*handler)(int, siginfo_t*, void*); +} old_low_level_signal_handler_states[NSIG]; + +void +uninstall_low_level_interrupt_handlers_atexit(void) +{ + int signal; + for (signal = 0; signal < NSIG; ++signal) { + struct low_level_signal_handler_state + *old_low_level_signal_handler_state = + old_low_level_signal_handler_states + signal; + if (old_low_level_signal_handler_state->was_modified) { + struct sigaction sa; + sa.sa_sigaction = old_low_level_signal_handler_state->handler; + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_SIGINFO | SA_RESTART; + sigaction(signal, &sa, NULL); + } + } +} + +/* Undoably install a special low-level handler for signal; or if + * handler is SIG_DFL, remove any special handling for signal. + * + * The "undoably" aspect is because we also arrange with atexit() for + * the handler to be restored to its old value. This is for tidiness: + * it shouldn't matter much ordinarily, but it does remove a window + * where e.g. memory fault signals (SIGSEGV or SIGBUS, which in + * ordinary operation of SBCL are sent to the generational garbage + * collector, then possibly onward to Lisp code) or SIGINT (which is + * ordinarily passed to Lisp code) could otherwise be handled + * bizarrely/brokenly because the Lisp code would try to deal with + * them using machinery (like stream output buffers) which has already + * been dismantled. */ void -interrupt_install_low_level_handler (int signal, - void handler(int, siginfo_t*, void*)) +undoably_install_low_level_interrupt_handler (int signal, + void handler(int, + siginfo_t*, + void*)) { struct sigaction sa; + struct low_level_signal_handler_state *old_low_level_signal_handler_state = + old_low_level_signal_handler_states + signal; + + if (0 > signal || signal >= NSIG) { + lose("bad signal number %d", signal); + } sa.sa_sigaction = handler; sigemptyset(&sa.sa_mask); sigaddset_blockable(&sa.sa_mask); sa.sa_flags = SA_SIGINFO | SA_RESTART; - sigaction(signal, &sa, NULL); + /* In the case of interrupt handlers which are modified more than + * once, we only save the original unmodified copy. */ + if (!old_low_level_signal_handler_state->was_modified) { + struct sigaction *old_handler = + (struct sigaction*) &old_low_level_signal_handler_state->handler; + old_low_level_signal_handler_state->was_modified = 1; + sigaction(signal, &sa, old_handler); + } else { + sigaction(signal, &sa, NULL); + } + interrupt_low_level_handlers[signal] = - (ARE_SAME_HANDLER(handler,SIG_DFL) ? 0 : handler); + (ARE_SAME_HANDLER(handler, SIG_DFL) ? 0 : handler); } /* This is called from Lisp. */ @@ -536,7 +649,7 @@ install_handler(int signal, void handler(int, siginfo_t*, void*)) sigset_t old, new; union interrupt_handler oldhandler; - FSHOW((stderr, "entering POSIX install_handler(%d, ..)\n", signal)); + FSHOW((stderr, "/entering POSIX install_handler(%d, ..)\n", signal)); sigemptyset(&new); sigaddset(&new, signal); @@ -545,7 +658,7 @@ install_handler(int signal, void handler(int, siginfo_t*, void*)) sigemptyset(&new); sigaddset_blockable(&new); - FSHOW((stderr, "interrupt_low_level_handlers[signal]=%d\n", + FSHOW((stderr, "/interrupt_low_level_handlers[signal]=%d\n", interrupt_low_level_handlers[signal])); if (interrupt_low_level_handlers[signal]==0) { if (ARE_SAME_HANDLER(handler, SIG_DFL) || @@ -569,7 +682,7 @@ install_handler(int signal, void handler(int, siginfo_t*, void*)) sigprocmask(SIG_SETMASK, &old, 0); - FSHOW((stderr, "leaving POSIX install_handler(%d, ..)\n", signal)); + FSHOW((stderr, "/leaving POSIX install_handler(%d, ..)\n", signal)); return (unsigned long)oldhandler.lisp; } @@ -579,6 +692,12 @@ interrupt_init(void) { int i; + SHOW("entering interrupt_init()"); + + /* Set up for recovery from any installed low-level handlers. */ + atexit(&uninstall_low_level_interrupt_handlers_atexit); + + /* Set up high level handler information. */ for (i = 0; i < NSIG; i++) { interrupt_handlers[i].c = /* (The cast here blasts away the distinction between @@ -588,4 +707,6 @@ interrupt_init(void) * 3-argument form is expected.) */ (void (*)(int, siginfo_t*, void*))SIG_DFL; } + + SHOW("returning from interrupt_init()"); }