diff options
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/libxl/libxl_event.c | 184 | ||||
| -rw-r--r-- | tools/libxl/libxl_internal.h | 8 |
2 files changed, 163 insertions, 29 deletions
diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c index 72cb72367d..b85dbf6d51 100644 --- a/tools/libxl/libxl_event.c +++ b/tools/libxl/libxl_event.c @@ -38,23 +38,131 @@ * The application's registration hooks should be called ONLY via * these macros, with the ctx locked. Likewise all the "occurred" * entrypoints from the application should assert(!in_hook); + * + * During the hook call - including while the arguments are being + * evaluated - ev->nexus is guaranteed to be valid and refer to the + * nexus which is being used for this event registration. The + * arguments should specify ev->nexus for the for_libxl argument and + * ev->nexus->for_app_reg (or a pointer to it) for for_app_reg. */ -#define OSEVENT_HOOK_INTERN(retval, hookname, ...) do { \ - if (CTX->osevent_hooks) { \ - CTX->osevent_in_hook++; \ - retval CTX->osevent_hooks->hookname(CTX->osevent_user, __VA_ARGS__); \ - CTX->osevent_in_hook--; \ - } \ +#define OSEVENT_HOOK_INTERN(retval, failedp, evkind, hookop, nexusop, ...) do { \ + if (CTX->osevent_hooks) { \ + CTX->osevent_in_hook++; \ + libxl__osevent_hook_nexi *nexi = &CTX->hook_##evkind##_nexi_idle; \ + osevent_hook_pre_##nexusop(gc, ev, nexi, &ev->nexus); \ + retval CTX->osevent_hooks->evkind##_##hookop \ + (CTX->osevent_user, __VA_ARGS__); \ + if ((failedp)) \ + osevent_hook_failed_##nexusop(gc, ev, nexi, &ev->nexus); \ + CTX->osevent_in_hook--; \ + } \ } while (0) -#define OSEVENT_HOOK(hookname, ...) ({ \ - int osevent_hook_rc = 0; \ - OSEVENT_HOOK_INTERN(osevent_hook_rc = , hookname, __VA_ARGS__); \ - osevent_hook_rc; \ +#define OSEVENT_HOOK(evkind, hookop, nexusop, ...) ({ \ + int osevent_hook_rc = 0; \ + OSEVENT_HOOK_INTERN(osevent_hook_rc =, !!osevent_hook_rc, \ + evkind, hookop, nexusop, __VA_ARGS__); \ + osevent_hook_rc; \ }) -#define OSEVENT_HOOK_VOID(hookname, ...) \ - OSEVENT_HOOK_INTERN(/* void */, hookname, __VA_ARGS__) +#define OSEVENT_HOOK_VOID(evkind, hookop, nexusop, ...) \ + OSEVENT_HOOK_INTERN(/* void */, 0, evkind, hookop, nexusop, __VA_ARGS__) + +/* + * The application's calls to libxl_osevent_occurred_... may be + * indefinitely delayed with respect to the rest of the program (since + * they are not necessarily called with any lock held). So the + * for_libxl value we receive may be (almost) arbitrarily old. All we + * know is that it came from this ctx. + * + * Therefore we may not free the object referred to by any for_libxl + * value until we free the whole libxl_ctx. And if we reuse it we + * must be able to tell when an old use turns up, and discard the + * stale event. + * + * Thus we cannot use the ev directly as the for_libxl value - we need + * a layer of indirection. + * + * We do this by keeping a pool of libxl__osevent_hook_nexus structs, + * and use pointers to them as for_libxl values. In fact, there are + * two pools: one for fds and one for timeouts. This ensures that we + * don't risk a type error when we upcast nexus->ev. In each nexus + * the ev is either null or points to a valid libxl__ev_time or + * libxl__ev_fd, as applicable. + * + * We /do/ allow ourselves to reassociate an old nexus with a new ev + * as otherwise we would have to leak nexi. (This reassociation + * might, of course, be an old ev being reused for a new purpose so + * simply comparing the ev pointer is not sufficient.) Thus the + * libxl_osevent_occurred functions need to check that the condition + * allegedly signalled by this event actually exists. + * + * The nexi and the lists are all protected by the ctx lock. + */ + +struct libxl__osevent_hook_nexus { + void *ev; + void *for_app_reg; + LIBXL_SLIST_ENTRY(libxl__osevent_hook_nexus) next; +}; + +static void *osevent_ev_from_hook_nexus(libxl_ctx *ctx, + libxl__osevent_hook_nexus *nexus /* pass void *for_libxl */) +{ + return nexus->ev; +} + +static void osevent_release_nexus(libxl__gc *gc, + libxl__osevent_hook_nexi *nexi_idle, + libxl__osevent_hook_nexus *nexus) +{ + nexus->ev = 0; + LIBXL_SLIST_INSERT_HEAD(nexi_idle, nexus, next); +} + +/*----- OSEVENT* hook functions for nexusop "alloc" -----*/ +static void osevent_hook_pre_alloc(libxl__gc *gc, void *ev, + libxl__osevent_hook_nexi *nexi_idle, + libxl__osevent_hook_nexus **nexus_r) +{ + libxl__osevent_hook_nexus *nexus = LIBXL_SLIST_FIRST(nexi_idle); + if (nexus) { + LIBXL_SLIST_REMOVE_HEAD(nexi_idle, next); + } else { + nexus = libxl__zalloc(NOGC, sizeof(*nexus)); + } + nexus->ev = ev; + *nexus_r = nexus; +} +static void osevent_hook_failed_alloc(libxl__gc *gc, void *ev, + libxl__osevent_hook_nexi *nexi_idle, + libxl__osevent_hook_nexus **nexus) +{ + osevent_release_nexus(gc, nexi_idle, *nexus); +} + +/*----- OSEVENT* hook functions for nexusop "release" -----*/ +static void osevent_hook_pre_release(libxl__gc *gc, void *ev, + libxl__osevent_hook_nexi *nexi_idle, + libxl__osevent_hook_nexus **nexus) +{ + osevent_release_nexus(gc, nexi_idle, *nexus); +} +static void osevent_hook_failed_release(libxl__gc *gc, void *ev, + libxl__osevent_hook_nexi *nexi_idle, + libxl__osevent_hook_nexus **nexus) +{ + abort(); +} + +/*----- OSEVENT* hook functions for nexusop "noop" -----*/ +static void osevent_hook_pre_noop(libxl__gc *gc, void *ev, + libxl__osevent_hook_nexi *nexi_idle, + libxl__osevent_hook_nexus **nexus) { } +static void osevent_hook_failed_noop(libxl__gc *gc, void *ev, + libxl__osevent_hook_nexi *nexi_idle, + libxl__osevent_hook_nexus **nexus) { } + /* * fd events @@ -72,7 +180,8 @@ int libxl__ev_fd_register(libxl__gc *gc, libxl__ev_fd *ev, DBG("ev_fd=%p register fd=%d events=%x", ev, fd, events); - rc = OSEVENT_HOOK(fd_register, fd, &ev->for_app_reg, events, ev); + rc = OSEVENT_HOOK(fd,register, alloc, fd, &ev->nexus->for_app_reg, + events, ev->nexus); if (rc) goto out; ev->fd = fd; @@ -97,7 +206,7 @@ int libxl__ev_fd_modify(libxl__gc *gc, libxl__ev_fd *ev, short events) DBG("ev_fd=%p modify fd=%d events=%x", ev, ev->fd, events); - rc = OSEVENT_HOOK(fd_modify, ev->fd, &ev->for_app_reg, events); + rc = OSEVENT_HOOK(fd,modify, noop, ev->fd, &ev->nexus->for_app_reg, events); if (rc) goto out; ev->events = events; @@ -119,7 +228,7 @@ void libxl__ev_fd_deregister(libxl__gc *gc, libxl__ev_fd *ev) DBG("ev_fd=%p deregister fd=%d", ev, ev->fd); - OSEVENT_HOOK_VOID(fd_deregister, ev->fd, ev->for_app_reg); + OSEVENT_HOOK_VOID(fd,deregister, release, ev->fd, ev->nexus->for_app_reg); LIBXL_LIST_REMOVE(ev, entry); ev->fd = -1; @@ -171,7 +280,8 @@ static int time_register_finite(libxl__gc *gc, libxl__ev_time *ev, { int rc; - rc = OSEVENT_HOOK(timeout_register, &ev->for_app_reg, absolute, ev); + rc = OSEVENT_HOOK(timeout,register, alloc, &ev->nexus->for_app_reg, + absolute, ev->nexus); if (rc) return rc; ev->infinite = 0; @@ -184,7 +294,7 @@ static int time_register_finite(libxl__gc *gc, libxl__ev_time *ev, static void time_deregister(libxl__gc *gc, libxl__ev_time *ev) { if (!ev->infinite) { - OSEVENT_HOOK_VOID(timeout_deregister, ev->for_app_reg); + OSEVENT_HOOK_VOID(timeout,deregister, release, ev->nexus->for_app_reg); LIBXL_TAILQ_REMOVE(&CTX->etimes, ev, entry); } } @@ -270,7 +380,8 @@ int libxl__ev_time_modify_abs(libxl__gc *gc, libxl__ev_time *ev, rc = time_register_finite(gc, ev, absolute); if (rc) goto out; } else { - rc = OSEVENT_HOOK(timeout_modify, &ev->for_app_reg, absolute); + rc = OSEVENT_HOOK(timeout,modify, noop, + &ev->nexus->for_app_reg, absolute); if (rc) goto out; LIBXL_TAILQ_REMOVE(&CTX->etimes, ev, entry); @@ -1010,35 +1121,54 @@ void libxl_osevent_register_hooks(libxl_ctx *ctx, void libxl_osevent_occurred_fd(libxl_ctx *ctx, void *for_libxl, - int fd, short events, short revents) + int fd, short events_ign, short revents_ign) { - libxl__ev_fd *ev = for_libxl; - EGC_INIT(ctx); CTX_LOCK; assert(!CTX->osevent_in_hook); - assert(fd == ev->fd); - revents &= ev->events; - if (revents) - ev->func(egc, ev, fd, ev->events, revents); + libxl__ev_fd *ev = osevent_ev_from_hook_nexus(ctx, for_libxl); + if (!ev) goto out; + if (ev->fd != fd) goto out; + struct pollfd check; + for (;;) { + check.fd = fd; + check.events = ev->events; + int r = poll(&check, 1, 0); + if (!r) + goto out; + if (r==1) + break; + assert(r<0); + if (errno != EINTR) { + LIBXL__EVENT_DISASTER(egc, "failed poll to check for fd", errno, 0); + goto out; + } + } + + if (check.revents) + ev->func(egc, ev, fd, ev->events, check.revents); + + out: CTX_UNLOCK; EGC_FREE; } void libxl_osevent_occurred_timeout(libxl_ctx *ctx, void *for_libxl) { - libxl__ev_time *ev = for_libxl; - EGC_INIT(ctx); CTX_LOCK; assert(!CTX->osevent_in_hook); + libxl__ev_time *ev = osevent_ev_from_hook_nexus(ctx, for_libxl); + if (!ev) goto out; assert(!ev->infinite); + LIBXL_TAILQ_REMOVE(&CTX->etimes, ev, entry); ev->func(egc, ev, &ev->abs); + out: CTX_UNLOCK; EGC_FREE; } diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h index 0b38e3e8bc..1567b4b03f 100644 --- a/tools/libxl/libxl_internal.h +++ b/tools/libxl/libxl_internal.h @@ -136,6 +136,8 @@ typedef struct libxl__gc libxl__gc; typedef struct libxl__egc libxl__egc; typedef struct libxl__ao libxl__ao; typedef struct libxl__aop_occurred libxl__aop_occurred; +typedef struct libxl__osevent_hook_nexus libxl__osevent_hook_nexus; +typedef struct libxl__osevent_hook_nexi libxl__osevent_hook_nexi; _hidden void libxl__alloc_failed(libxl_ctx *, const char *func, size_t nmemb, size_t size) __attribute__((noreturn)); @@ -163,7 +165,7 @@ struct libxl__ev_fd { libxl__ev_fd_callback *func; /* remainder is private for libxl__ev_fd... */ LIBXL_LIST_ENTRY(libxl__ev_fd) entry; - void *for_app_reg; + libxl__osevent_hook_nexus *nexus; }; @@ -178,7 +180,7 @@ struct libxl__ev_time { int infinite; /* not registered in list or with app if infinite */ LIBXL_TAILQ_ENTRY(libxl__ev_time) entry; struct timeval abs; - void *for_app_reg; + libxl__osevent_hook_nexus *nexus; }; typedef struct libxl__ev_xswatch libxl__ev_xswatch; @@ -329,6 +331,8 @@ struct libxl__ctx { libxl__poller poller_app; /* libxl_osevent_beforepoll and _afterpoll */ LIBXL_LIST_HEAD(, libxl__poller) pollers_event, pollers_idle; + LIBXL_SLIST_HEAD(libxl__osevent_hook_nexi, libxl__osevent_hook_nexus) + hook_fd_nexi_idle, hook_timeout_nexi_idle; LIBXL_LIST_HEAD(, libxl__ev_fd) efds; LIBXL_TAILQ_HEAD(, libxl__ev_time) etimes; |