selftests/bpf: add read_with_timeout() utility function

int read_with_timeout(int fd, char *buf, size_t count, long usec)

As a regular read(2), but allows to specify a timeout in
micro-seconds. Returns -EAGAIN on timeout.
Implemented using select().

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20241112110906.3045278-3-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2024-11-12 03:09:04 -08:00 committed by Alexei Starovoitov
parent d9d4d127e8
commit 03066ed310
3 changed files with 29 additions and 0 deletions

View File

@ -742,6 +742,7 @@ TRUNNER_EXTRA_SOURCES := test_progs.c \
unpriv_helpers.c \
netlink_helpers.c \
jit_disasm_helpers.c \
io_helpers.c \
test_loader.c \
xsk.c \
disasm.c \

View File

@ -0,0 +1,21 @@
// SPDX-License-Identifier: GPL-2.0
#include <sys/select.h>
#include <unistd.h>
#include <errno.h>
int read_with_timeout(int fd, char *buf, size_t count, long usec)
{
const long M = 1000 * 1000;
struct timeval tv = { usec / M, usec % M };
fd_set fds;
int err;
FD_ZERO(&fds);
FD_SET(fd, &fds);
err = select(fd + 1, &fds, NULL, NULL, &tv);
if (err < 0)
return err;
if (FD_ISSET(fd, &fds))
return read(fd, buf, count);
return -EAGAIN;
}

View File

@ -0,0 +1,7 @@
// SPDX-License-Identifier: GPL-2.0
#include <unistd.h>
/* As a regular read(2), but allows to specify a timeout in micro-seconds.
* Returns -EAGAIN on timeout.
*/
int read_with_timeout(int fd, char *buf, size_t count, long usec);