This example is missing a few fixes that are in the liburing version,
synchronize with the upstream version.

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

It would seem none of the kernel continuous integration does this:
    $ cd tools/io_uring
    $ make

Otherwise it may have noticed:
   cc -Wall -Wextra -g -D_GNU_SOURCE   -c -o io_uring-bench.o
	 io_uring-bench.c
io_uring-bench.c:133:12: error: static declaration of ‘gettid’
	 follows non-static declaration
  133 | static int gettid(void)
      |            ^~~~~~
In file included from /usr/include/unistd.h:1170,
                 from io_uring-bench.c:27:
/usr/include/x86_64-linux-gnu/bits/unistd_ext.h:34:16: note:
	 previous declaration of ‘gettid’ was here
   34 | extern __pid_t gettid (void) __THROW;
      |                ^~~~~~
make: *** [<builtin>: io_uring-bench.o] Error 1

The problem on Ubuntu 20.04 (with lk 5.9.0-rc5) is that unistd.h
already defines gettid(). So prefix the local definition with
"lk_".

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

poll events should be 32-bits to cover EPOLLEXCLUSIVE.

Explicit word-swap the poll32_events for big endian to make sure the ABI
is not changed.  We call this feature IORING_FEAT_POLL_32BITS,
applications who want to use EPOLLEXCLUSIVE should check the feature bit
first.

Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Various fixes and changes have been applied to liburing since we
copied some select bits to the kernel testing/examples part, sync
up with liburing to get those changes.

Most notable is the change that split the CQE reading into the peek
and seen event, instead of being just a single function. Also fixes
an unsigned wrap issue in io_uring_submit(), leak of 'fd' in setup
if we fail, and various other little issues.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Currently fails with:

io_uring-bench.o: In function `main':
/home/axboe/git/linux-block/tools/io_uring/io_uring-bench.c:560: undefined reference to `pthread_create'
/home/axboe/git/linux-block/tools/io_uring/io_uring-bench.c:588: undefined reference to `pthread_join'
collect2: error: ld returned 1 exit status
Makefile:11: recipe for target 'io_uring-bench' failed
make: *** [io_uring-bench] Error 1

Move -lpthread to the end.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

This ended up not being included in the mainline version of io_uring,
so drop it from the test app as well.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

This adds two test programs in tools/io_uring/ that demonstrate both
the raw io_uring API (and all features) through a small benchmark
app, io_uring-bench, and the liburing exposed API in a simplified
cp(1) implementation through io_uring-cp.

Signed-off-by: Jens Axboe <axboe@kernel.dk>