From: Stefan Hajnoczi Date: Mon, 11 May 2020 19:36:29 +0100 Subject: [PATCH] aio-posix: don't duplicate fd handler deletion in fdmon_io_uring_destroy() The io_uring file descriptor monitoring implementation has an internal list of fd handlers that are pending submission to io_uring. fdmon_io_uring_destroy() deletes all fd handlers on the list. Don't delete fd handlers directly in fdmon_io_uring_destroy() for two reasons: 1. This duplicates the aio-posix.c AioHandler deletion code and could become outdated if the struct changes. 2. Only handlers with the FDMON_IO_URING_REMOVE flag set are safe to remove. If the flag is not set then something still has a pointer to the fd handler. Let aio-posix.c and its user worry about that. In practice this isn't an issue because fdmon_io_uring_destroy() is only called when shutting down so all users have removed their fd handlers, but the next patch will need this! Signed-off-by: Stefan Hajnoczi --- util/aio-posix.c | 1 + util/fdmon-io_uring.c | 13 ++++++++++--- 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/util/aio-posix.c b/util/aio-posix.c index c3613d299e..8af334ab19 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -679,6 +679,7 @@ void aio_context_destroy(AioContext *ctx) { fdmon_io_uring_destroy(ctx); fdmon_epoll_disable(ctx); + aio_free_deleted_handlers(ctx); } void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns, diff --git a/util/fdmon-io_uring.c b/util/fdmon-io_uring.c index d5a80ed6fb..1d14177df0 100644 --- a/util/fdmon-io_uring.c +++ b/util/fdmon-io_uring.c @@ -342,11 +342,18 @@ void fdmon_io_uring_destroy(AioContext *ctx) io_uring_queue_exit(&ctx->fdmon_io_uring); - /* No need to submit these anymore, just free them. */ + /* Move handlers due to be removed onto the deleted list */ while ((node = QSLIST_FIRST_RCU(&ctx->submit_list))) { + unsigned flags = atomic_fetch_and(&node->flags, + ~(FDMON_IO_URING_PENDING | + FDMON_IO_URING_ADD | + FDMON_IO_URING_REMOVE)); + + if (flags & FDMON_IO_URING_REMOVE) { + QLIST_INSERT_HEAD_RCU(&ctx->deleted_aio_handlers, node, node_deleted); + } + QSLIST_REMOVE_HEAD_RCU(&ctx->submit_list, node_submitted); - QLIST_REMOVE(node, node); - g_free(node); } ctx->fdmon_ops = &fdmon_poll_ops;