diff options
Diffstat (limited to 'lib/tevent/tevent_signal.c')
| -rw-r--r-- | lib/tevent/tevent_signal.c | 291 |
1 files changed, 291 insertions, 0 deletions
diff --git a/lib/tevent/tevent_signal.c b/lib/tevent/tevent_signal.c new file mode 100644 index 0000000000..36907af6be --- /dev/null +++ b/lib/tevent/tevent_signal.c @@ -0,0 +1,291 @@ +/* + Unix SMB/CIFS implementation. + + common events code for signal events + + Copyright (C) Andrew Tridgell 2007 + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. +*/ + +#include <signal.h> +#include "replace.h" +#include "system/filesys.h" +#include "system/select.h" +#include "tevent.h" +#include "tevent_internal.h" +#include "tevent_util.h" + +#define NUM_SIGNALS 64 + +/* maximum number of SA_SIGINFO signals to hold in the queue */ +#define SA_INFO_QUEUE_COUNT 10 + +struct sigcounter { + uint32_t count; + uint32_t seen; +}; + +#define SIG_INCREMENT(s) (s).count++ +#define SIG_SEEN(s, n) (s).seen += (n) +#define SIG_PENDING(s) ((s).seen != (s).count) + + +/* + the poor design of signals means that this table must be static global +*/ +static struct sig_state { + struct signal_event *sig_handlers[NUM_SIGNALS+1]; + struct sigaction *oldact[NUM_SIGNALS+1]; + struct sigcounter signal_count[NUM_SIGNALS+1]; + struct sigcounter got_signal; + int pipe_hack[2]; +#ifdef SA_SIGINFO + /* with SA_SIGINFO we get quite a lot of info per signal */ + siginfo_t *sig_info[NUM_SIGNALS+1]; + struct sigcounter sig_blocked[NUM_SIGNALS+1]; +#endif +} *sig_state; + +/* + return number of sigcounter events not processed yet +*/ +static uint32_t sig_count(struct sigcounter s) +{ + if (s.count >= s.seen) { + return s.count - s.seen; + } + return 1 + (0xFFFFFFFF & ~(s.seen - s.count)); +} + +/* + signal handler - redirects to registered signals +*/ +static void signal_handler(int signum) +{ + char c = 0; + SIG_INCREMENT(sig_state->signal_count[signum]); + SIG_INCREMENT(sig_state->got_signal); + /* doesn't matter if this pipe overflows */ + write(sig_state->pipe_hack[1], &c, 1); +} + +#ifdef SA_SIGINFO +/* + signal handler with SA_SIGINFO - redirects to registered signals +*/ +static void signal_handler_info(int signum, siginfo_t *info, void *uctx) +{ + uint32_t count = sig_count(sig_state->signal_count[signum]); + sig_state->sig_info[signum][count] = *info; + + signal_handler(signum); + + /* handle SA_SIGINFO */ + if (count+1 == SA_INFO_QUEUE_COUNT) { + /* we've filled the info array - block this signal until + these ones are delivered */ + sigset_t set; + sigemptyset(&set); + sigaddset(&set, signum); + sigprocmask(SIG_BLOCK, &set, NULL); + SIG_INCREMENT(sig_state->sig_blocked[signum]); + } +} +#endif + +/* + destroy a signal event +*/ +static int signal_event_destructor(struct signal_event *se) +{ + se->event_ctx->num_signal_handlers--; + DLIST_REMOVE(sig_state->sig_handlers[se->signum], se); + if (sig_state->sig_handlers[se->signum] == NULL) { + /* restore old handler, if any */ + sigaction(se->signum, sig_state->oldact[se->signum], NULL); + sig_state->oldact[se->signum] = NULL; +#ifdef SA_SIGINFO + if (se->sa_flags & SA_SIGINFO) { + talloc_free(sig_state->sig_info[se->signum]); + sig_state->sig_info[se->signum] = NULL; + } +#endif + } + return 0; +} + +/* + this is part of the pipe hack needed to avoid the signal race condition +*/ +static void signal_pipe_handler(struct event_context *ev, struct fd_event *fde, + uint16_t flags, void *private) +{ + char c[16]; + /* its non-blocking, doesn't matter if we read too much */ + read(sig_state->pipe_hack[0], c, sizeof(c)); +} + +/* + add a signal event + return NULL on failure (memory allocation error) +*/ +struct signal_event *common_event_add_signal(struct event_context *ev, + TALLOC_CTX *mem_ctx, + int signum, + int sa_flags, + event_signal_handler_t handler, + void *private_data) +{ + struct signal_event *se; + + if (signum >= NUM_SIGNALS) { + return NULL; + } + + /* the sig_state needs to be on a global context as it can last across + multiple event contexts */ + if (sig_state == NULL) { + sig_state = talloc_zero(talloc_autofree_context(), struct sig_state); + if (sig_state == NULL) { + return NULL; + } + } + + se = talloc(mem_ctx?mem_ctx:ev, struct signal_event); + if (se == NULL) return NULL; + + se->event_ctx = ev; + se->handler = handler; + se->private_data = private_data; + se->signum = signum; + se->sa_flags = sa_flags; + + /* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */ + if (!talloc_reference(se, sig_state)) { + return NULL; + } + + /* only install a signal handler if not already installed */ + if (sig_state->sig_handlers[signum] == NULL) { + struct sigaction act; + ZERO_STRUCT(act); + act.sa_handler = signal_handler; + act.sa_flags = sa_flags; +#ifdef SA_SIGINFO + if (sa_flags & SA_SIGINFO) { + act.sa_handler = NULL; + act.sa_sigaction = signal_handler_info; + if (sig_state->sig_info[signum] == NULL) { + sig_state->sig_info[signum] = talloc_array(sig_state, siginfo_t, SA_INFO_QUEUE_COUNT); + if (sig_state->sig_info[signum] == NULL) { + talloc_free(se); + return NULL; + } + } + } +#endif + sig_state->oldact[signum] = talloc(sig_state, struct sigaction); + if (sig_state->oldact[signum] == NULL) { + talloc_free(se); + return NULL; + } + if (sigaction(signum, &act, sig_state->oldact[signum]) == -1) { + talloc_free(se); + return NULL; + } + } + + DLIST_ADD(sig_state->sig_handlers[signum], se); + + talloc_set_destructor(se, signal_event_destructor); + + /* we need to setup the pipe hack handler if not already + setup */ + if (ev->pipe_fde == NULL) { + if (sig_state->pipe_hack[0] == 0 && + sig_state->pipe_hack[1] == 0) { + pipe(sig_state->pipe_hack); + ev_set_blocking(sig_state->pipe_hack[0], false); + ev_set_blocking(sig_state->pipe_hack[1], false); + } + ev->pipe_fde = event_add_fd(ev, ev, sig_state->pipe_hack[0], + EVENT_FD_READ, signal_pipe_handler, NULL); + } + ev->num_signal_handlers++; + + return se; +} + + +/* + check if a signal is pending + return != 0 if a signal was pending +*/ +int common_event_check_signal(struct event_context *ev) +{ + int i; + + if (!sig_state || !SIG_PENDING(sig_state->got_signal)) { + return 0; + } + + for (i=0;i<NUM_SIGNALS+1;i++) { + struct signal_event *se, *next; + struct sigcounter counter = sig_state->signal_count[i]; + uint32_t count = sig_count(counter); + + if (count == 0) { + continue; + } + for (se=sig_state->sig_handlers[i];se;se=next) { + next = se->next; +#ifdef SA_SIGINFO + if (se->sa_flags & SA_SIGINFO) { + int j; + for (j=0;j<count;j++) { + /* note the use of the sig_info array as a + ring buffer */ + int ofs = ((count-1) + j) % SA_INFO_QUEUE_COUNT; + se->handler(ev, se, i, 1, + (void*)&sig_state->sig_info[i][ofs], + se->private_data); + } + if (SIG_PENDING(sig_state->sig_blocked[i])) { + /* we'd filled the queue, unblock the + signal now */ + sigset_t set; + sigemptyset(&set); + sigaddset(&set, i); + SIG_SEEN(sig_state->sig_blocked[i], + sig_count(sig_state->sig_blocked[i])); + sigprocmask(SIG_UNBLOCK, &set, NULL); + } + if (se->sa_flags & SA_RESETHAND) { + talloc_free(se); + } + continue; + } +#endif + se->handler(ev, se, i, count, NULL, se->private_data); + if (se->sa_flags & SA_RESETHAND) { + talloc_free(se); + } + } + SIG_SEEN(sig_state->signal_count[i], count); + SIG_SEEN(sig_state->got_signal, count); + } + + return 1; +} |