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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   become outdated if the struct changes.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 <stefanha@redhat.com>
Tested-by: Oleksandr Natalenko <oleksandr@redhat.com>
Message-id: 20200511183630.279750-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2020-05-11 19:36:29 +01:00
parent 6fb5f0842a
commit de137e44f7
2 changed files with 11 additions and 3 deletions
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1
util/aio-posix.c
View File

@ -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,

13
util/fdmon-io_uring.c
View File

@ -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;