From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54507) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a1HvE-0001gM-Dl for qemu-devel@nongnu.org; Tue, 24 Nov 2015 13:02:35 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a1Hv9-00062E-U1 for qemu-devel@nongnu.org; Tue, 24 Nov 2015 13:02:32 -0500 From: Paolo Bonzini Date: Tue, 24 Nov 2015 19:01:16 +0100 Message-Id: <1448388091-117282-26-git-send-email-pbonzini@redhat.com> In-Reply-To: <1448388091-117282-1-git-send-email-pbonzini@redhat.com> References: <1448388091-117282-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH 25/40] aio-posix: remove walking_handlers, protecting AioHandler list with list_lock List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, qemu-block@nongnu.org Signed-off-by: Paolo Bonzini --- aio-posix.c | 55 +++++++++++++++++++++++++++++++++---------------------- 1 file changed, 33 insertions(+), 22 deletions(-) diff --git a/aio-posix.c b/aio-posix.c index 370fefe..212c203 100644 --- a/aio-posix.c +++ b/aio-posix.c @@ -15,7 +15,7 @@ #include "qemu-common.h" #include "block/block.h" -#include "qemu/queue.h" +#include "qemu/rcu_queue.h" #include "qemu/sockets.h" #ifdef CONFIG_EPOLL #include @@ -212,6 +212,8 @@ void aio_set_fd_handler(AioContext *ctx, bool is_new = false; bool deleted = false; + qemu_lockcnt_lock(&ctx->list_lock); + node = find_aio_handler(ctx, fd); /* Are we deleting the fd handler? */ @@ -219,14 +221,14 @@ void aio_set_fd_handler(AioContext *ctx, if (node) { g_source_remove_poll(&ctx->source, &node->pfd); - /* If the lock is held, just mark the node as deleted */ - if (ctx->walking_handlers) { + /* If aio_poll is in progress, just mark the node as deleted */ + if (qemu_lockcnt_count(&ctx->list_lock)) { node->deleted = 1; node->pfd.revents = 0; } else { /* Otherwise, delete it for real. We can't just mark it as * deleted because deleted nodes are only cleaned up after - * releasing the walking_handlers lock. + * releasing the list_lock. */ QLIST_REMOVE(node, node); deleted = true; @@ -237,7 +239,7 @@ void aio_set_fd_handler(AioContext *ctx, /* Alloc and insert if it's not already there */ node = g_new0(AioHandler, 1); node->pfd.fd = fd; - QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node); + QLIST_INSERT_HEAD_RCU(&ctx->aio_handlers, node, node); g_source_add_poll(&ctx->source, &node->pfd); is_new = true; @@ -253,6 +255,7 @@ void aio_set_fd_handler(AioContext *ctx, } aio_epoll_update(ctx, node, is_new); + qemu_lockcnt_unlock(&ctx->list_lock); aio_notify(ctx); if (deleted) { g_free(node); @@ -276,20 +279,30 @@ bool aio_prepare(AioContext *ctx) bool aio_pending(AioContext *ctx) { AioHandler *node; + bool result = false; - QLIST_FOREACH(node, &ctx->aio_handlers, node) { + /* + * We have to walk very carefully in case aio_set_fd_handler is + * called while we're walking. + */ + qemu_lockcnt_inc(&ctx->list_lock); + + QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { int revents; revents = node->pfd.revents & node->pfd.events; if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read) { - return true; + result = true; + break; } if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write) { - return true; + result = true; + break; } } + qemu_lockcnt_dec(&ctx->list_lock); - return false; + return result; } bool aio_dispatch(AioContext *ctx) @@ -310,13 +323,12 @@ bool aio_dispatch(AioContext *ctx) * We have to walk very carefully in case aio_set_fd_handler is * called while we're walking. */ - ctx->walking_handlers++; + qemu_lockcnt_inc(&ctx->list_lock); - QLIST_FOREACH_SAFE(node, &ctx->aio_handlers, node, tmp) { + QLIST_FOREACH_SAFE_RCU(node, &ctx->aio_handlers, node, tmp) { int revents; - revents = node->pfd.revents & node->pfd.events; - node->pfd.revents = 0; + revents = atomic_xchg(&node->pfd.revents, 0) & node->pfd.events; if (!node->deleted && (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR)) && @@ -336,15 +348,15 @@ bool aio_dispatch(AioContext *ctx) } if (node->deleted) { - ctx->walking_handlers--; - if (!ctx->walking_handlers) { + if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) { + QLIST_REMOVE(node, node); g_free(node); + qemu_lockcnt_inc_and_unlock(&ctx->list_lock); } - ctx->walking_handlers++; } } - ctx->walking_handlers--; + qemu_lockcnt_dec(&ctx->list_lock); /* Run our timers */ progress |= timerlistgroup_run_timers(&ctx->tlg); @@ -419,12 +431,11 @@ bool aio_poll(AioContext *ctx, bool blocking) atomic_add(&ctx->notify_me, 2); } - ctx->walking_handlers++; - + qemu_lockcnt_inc(&ctx->list_lock); assert(npfd == 0); /* fill pollfds */ - QLIST_FOREACH(node, &ctx->aio_handlers, node) { + QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) { if (!node->deleted && node->pfd.events && !aio_epoll_enabled(ctx) && aio_node_check(ctx, node->is_external)) { @@ -461,12 +472,12 @@ bool aio_poll(AioContext *ctx, bool blocking) /* if we have any readable fds, dispatch event */ if (ret > 0) { for (i = 0; i < npfd; i++) { - nodes[i]->pfd.revents = pollfds[i].revents; + atomic_or(&nodes[i]->pfd.revents, pollfds[i].revents); } } npfd = 0; - ctx->walking_handlers--; + qemu_lockcnt_dec(&ctx->list_lock); /* Run dispatch even if there were no readable fds to run timers */ if (aio_dispatch(ctx)) { -- 1.8.3.1