diff options
| author | Stefan Hajnoczi <stefanha@redhat.com> | 2020-03-05 17:08:05 +0000 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2020-03-09 16:41:31 +0000 |
| commit | aa38e19f05c3a5ae64dff84f44e1aa31281a5b14 (patch) | |
| tree | 511a1cbddc11aee4e8b4ff22469189136cc125d9 /util/aio-posix.c | |
| parent | 73fd282e7b6dd4e4ea1c3bbb3d302c8db51e4ccf (diff) | |
aio-posix: support userspace polling of fd monitoring
Unlike ppoll(2) and epoll(7), Linux io_uring completions can be polled
from userspace. Previously userspace polling was only allowed when all
AioHandler's had an ->io_poll() callback. This prevented starvation of
fds by userspace pollable handlers.
Add the FDMonOps->need_wait() callback that enables userspace polling
even when some AioHandlers lack ->io_poll().
For example, it's now possible to do userspace polling when a TCP/IP
socket is monitored thanks to Linux io_uring.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://lore.kernel.org/r/20200305170806.1313245-7-stefanha@redhat.com
Message-Id: <20200305170806.1313245-7-stefanha@redhat.com>
Diffstat (limited to 'util/aio-posix.c')
| -rw-r--r-- | util/aio-posix.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/util/aio-posix.c b/util/aio-posix.c index ffd9cc381b..759989b45b 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -22,6 +22,11 @@ #include "trace.h" #include "aio-posix.h" +bool aio_poll_disabled(AioContext *ctx) +{ + return atomic_read(&ctx->poll_disable_cnt); +} + void aio_add_ready_handler(AioHandlerList *ready_list, AioHandler *node, int revents) @@ -423,7 +428,7 @@ static bool run_poll_handlers(AioContext *ctx, int64_t max_ns, int64_t *timeout) elapsed_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - start_time; max_ns = qemu_soonest_timeout(*timeout, max_ns); assert(!(max_ns && progress)); - } while (elapsed_time < max_ns && !atomic_read(&ctx->poll_disable_cnt)); + } while (elapsed_time < max_ns && !ctx->fdmon_ops->need_wait(ctx)); /* If time has passed with no successful polling, adjust *timeout to * keep the same ending time. @@ -451,7 +456,7 @@ static bool try_poll_mode(AioContext *ctx, int64_t *timeout) { int64_t max_ns = qemu_soonest_timeout(*timeout, ctx->poll_ns); - if (max_ns && !atomic_read(&ctx->poll_disable_cnt)) { + if (max_ns && !ctx->fdmon_ops->need_wait(ctx)) { poll_set_started(ctx, true); if (run_poll_handlers(ctx, max_ns, timeout)) { @@ -501,7 +506,7 @@ bool aio_poll(AioContext *ctx, bool blocking) /* If polling is allowed, non-blocking aio_poll does not need the * system call---a single round of run_poll_handlers_once suffices. */ - if (timeout || atomic_read(&ctx->poll_disable_cnt)) { + if (timeout || ctx->fdmon_ops->need_wait(ctx)) { ret = ctx->fdmon_ops->wait(ctx, &ready_list, timeout); } |