diff options
| -rw-r--r-- | src/sighook.c | 92 |
1 files changed, 51 insertions, 41 deletions
diff --git a/src/sighook.c b/src/sighook.c index 7897f42..ea58a0c 100644 --- a/src/sighook.c +++ b/src/sighook.c @@ -240,31 +240,52 @@ struct sighook { sighook_fn *fn; /** An argument to pass to the function. */ void *arg; + + /** The RCU pointer to this hook. */ + struct rcu *self; /** The next hook in the list. */ struct rcu next; }; -/** Add a hook to a linked list. */ -static void sigpush(struct rcu *rcu, struct sighook *hook) { - struct sighook *next = rcu_peek(rcu); - rcu_init(&hook->next, next); - rcu_update(rcu, hook); +/** + * An RCU-protected linked list of signal hooks. + */ +struct siglist { + /** The first hook in the list. */ + struct rcu head; + /** &last->next */ + struct rcu *tail; +}; + +/** Initialize a siglist. */ +static void siglist_init(struct siglist *list) { + rcu_init(&list->head, NULL); + list->tail = &list->head; +} + +/** Append a hook to a linked list. */ +static void sigpush(struct siglist *list, struct sighook *hook) { + hook->self = list->tail; + list->tail = &hook->next; + rcu_init(&hook->next, NULL); + rcu_update(hook->self, hook); } /** Remove a hook from the linked list. */ -static void sigpop(struct rcu *rcu, struct sighook *hook) { +static void sigpop(struct siglist *list, struct sighook *hook) { struct sighook *next = rcu_peek(&hook->next); - rcu_update(rcu, next); + rcu_update(hook->self, next); + if (next) { + next->self = hook->self; + } } /** The lists of signal hooks. */ -static struct rcu rcu_sighooks[64]; -/** The list of atsigexit() hooks. */ -static struct rcu rcu_exithooks; +static struct siglist sighooks[64]; /** Get the hook list for a particular signal. */ -static struct rcu *siglist(int sig) { - return &rcu_sighooks[sig % countof(rcu_sighooks)]; +static struct siglist *siglist(int sig) { + return &sighooks[sig % countof(sighooks)]; } /** Mutex for initialization and RCU writer exclusion. */ @@ -365,11 +386,11 @@ fail: } /** Find any matching hooks and run them. */ -static enum sigflags run_hooks(struct rcu *rcu, int sig, siginfo_t *info) { +static enum sigflags run_hooks(struct siglist *list, int sig, siginfo_t *info) { enum sigflags ret = 0; struct arc *slot = NULL; - struct sighook *hook = rcu_read(rcu, &slot); + struct sighook *hook = rcu_read(&list->head, &slot); while (hook) { if (hook->sig == sig || hook->sig == 0) { hook->fn(sig, info, hook->arg); @@ -407,12 +428,13 @@ static void sigdispatch(int sig, siginfo_t *info, void *context) { int error = errno; // Run the normal hooks - struct rcu *rcu = siglist(sig); - enum sigflags flags = run_hooks(rcu, sig, info); + struct siglist *list = siglist(sig); + enum sigflags flags = run_hooks(list, sig, info); // Run the atsigexit() hooks, if we're exiting if (!(flags & SH_CONTINUE) && is_fatal(sig)) { - run_hooks(&rcu_exithooks, sig, info); + list = siglist(0); + run_hooks(list, sig, info); reraise(sig); } @@ -435,10 +457,9 @@ static int siginit(int sig) { return -1; } - for (size_t i = 0; i < countof(rcu_sighooks); ++i) { - rcu_init(&rcu_sighooks[i], NULL); + for (size_t i = 0; i < countof(sighooks); ++i) { + siglist_init(&sighooks[i]); } - rcu_init(&rcu_exithooks, NULL); initialized = true; } @@ -462,7 +483,7 @@ static int siginit(int sig) { } /** Shared sighook()/atsigexit() implementation. */ -static struct sighook *sighook_impl(struct rcu *rcu, int sig, sighook_fn *fn, void *arg, enum sigflags flags) { +static struct sighook *sighook_impl(int sig, sighook_fn *fn, void *arg, enum sigflags flags) { struct sighook *hook = ALLOC(struct sighook); if (!hook) { return NULL; @@ -473,21 +494,21 @@ static struct sighook *sighook_impl(struct rcu *rcu, int sig, sighook_fn *fn, vo hook->fn = fn; hook->arg = arg; - sigpush(rcu, hook); + struct siglist *list = siglist(sig); + sigpush(list, hook); return hook; } struct sighook *sighook(int sig, sighook_fn *fn, void *arg, enum sigflags flags) { + bfs_assert(sig > 0); + mutex_lock(&sigmutex); struct sighook *ret = NULL; - if (siginit(sig) != 0) { - goto done; + if (siginit(sig) == 0) { + ret = sighook_impl(sig, fn, arg, flags); } - struct rcu *rcu = siglist(sig); - ret = sighook_impl(rcu, sig, fn, arg, flags); -done: mutex_unlock(&sigmutex); return ret; } @@ -508,7 +529,7 @@ struct sighook *atsigexit(sighook_fn *fn, void *arg) { } #endif - struct sighook *ret = sighook_impl(&rcu_exithooks, 0, fn, arg, 0); + struct sighook *ret = sighook_impl(0, fn, arg, 0); mutex_unlock(&sigmutex); return ret; } @@ -520,19 +541,8 @@ void sigunhook(struct sighook *hook) { mutex_lock(&sigmutex); - struct rcu *rcu; - if (hook->sig) { - rcu = siglist(hook->sig); - } else { - rcu = &rcu_exithooks; - } - - struct sighook *node = rcu_peek(rcu); - while (node != hook) { - rcu = &node->next; - node = rcu_peek(rcu); - } - sigpop(rcu, hook); + struct siglist *list = siglist(hook->sig); + sigpop(list, hook); mutex_unlock(&sigmutex); |