Messages in this thread Patch in this message | | | Date | Mon, 23 Feb 2004 16:01:48 -0800 | From | Andrew Morton <> | Subject | Re: /proc/kmsg blocks with O_NONBLOCK, read() should return 0 with EAGAIN |
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Graham Swallow <Information-Cascade@ntlworld.com> wrote: > > /proc/kmsg blocks with O_NONBLOCK, read() should return 0 with EAGAIN > > fd = open( "/proc/kmsg", O_RDONLY|O_NONBLOCK ); > ... > poll() -- says read it > > len = read(fd,buff,len); // first read is fine > ... > len = read(fd,buff,len); // second read blocks > > I call read() a second time, because I'm feeling lucky, > (this is library code, which also reads from sockets). > > I expected it to return 0 with errno==EAGAIN. > Instead it waits: do_syslog(2,buf,count); >
Does this work?
diff -puN fs/proc/kmsg.c~kmsg-nonblock fs/proc/kmsg.c --- 24/fs/proc/kmsg.c~kmsg-nonblock Mon Feb 23 16:00:48 2004 +++ 24-akpm/fs/proc/kmsg.c Mon Feb 23 16:01:12 2004 @@ -32,6 +32,8 @@ static int kmsg_release(struct inode * i static ssize_t kmsg_read(struct file * file, char * buf, size_t count, loff_t *ppos) { + if ((file->f_flags & O_NONBLOCK) && !do_syslog(9, 0, 0)) + return -EAGAIN; return do_syslog(2,buf,count); } _
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