flag parameters: NONBLOCK in timerfd_create

This patch adds support for the TFD_NONBLOCK flag to timerfd_create. The
additional changes needed are minimal.

The following test must be adjusted for architectures other than x86 and
x86-64 and in case the syscall numbers changed.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <fcntl.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>
#include <sys/syscall.h>

#ifndef __NR_timerfd_create
# ifdef __x86_64__
# define __NR_timerfd_create 283
# elif defined __i386__
# define __NR_timerfd_create 322
# else
# error "need __NR_timerfd_create"
# endif
#endif

#define TFD_NONBLOCK O_NONBLOCK

int
main (void)
{
int fd = syscall (__NR_timerfd_create, CLOCK_REALTIME, 0);
if (fd == -1)
{
puts ("timerfd_create(0) failed");
return 1;
}
int fl = fcntl (fd, F_GETFL);
if (fl == -1)
{
puts ("fcntl failed");
return 1;
}
if (fl & O_NONBLOCK)
{
puts ("timerfd_create(0) set non-blocking mode");
return 1;
}
close (fd);

fd = syscall (__NR_timerfd_create, CLOCK_REALTIME, TFD_NONBLOCK);
if (fd == -1)
{
puts ("timerfd_create(TFD_NONBLOCK) failed");
return 1;
}
fl = fcntl (fd, F_GETFL);
if (fl == -1)
{
puts ("fcntl failed");
return 1;
}
if ((fl & O_NONBLOCK) == 0)
{
puts ("timerfd_create(TFD_NONBLOCK) set non-blocking mode");
return 1;
}
close (fd);

puts ("OK");

return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Ulrich Drepper <[e-mail]>
Acked-by: Davide Libenzi <[e-mail]>
Cc: Michael Kerrisk <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/timerfd.c

···
 	int ufd;
 	struct timerfd_ctx *ctx;
 
-	if (flags & ~TFD_CLOEXEC)
+	if (flags & ~(TFD_CLOEXEC | TFD_NONBLOCK))
 		return -EINVAL;
 	if (clockid != CLOCK_MONOTONIC &&
 	    clockid != CLOCK_REALTIME)
···
 	hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
 
 	ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
-			       flags & O_CLOEXEC);
+			       flags & (O_CLOEXEC | O_NONBLOCK));
 	if (ufd < 0)
 		kfree(ctx);
 

include/linux/timerfd.h

···
 #ifndef _LINUX_TIMERFD_H
 #define _LINUX_TIMERFD_H
 
-/* For O_CLOEXEC */
+/* For O_CLOEXEC and O_NONBLOCK */
 #include <linux/fcntl.h>
 
 /* Flags for timerfd_settime.  */
···
 
 /* Flags for timerfd_create.  */
 #define TFD_CLOEXEC O_CLOEXEC
+#define TFD_NONBLOCK O_NONBLOCK
 
 
 #endif /* _LINUX_TIMERFD_H */