Messages in this thread | | | Date | Fri, 19 Sep 2003 09:06:46 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: use O_DIRECT open file, when read will hang. |
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On Fri, 19 Sep 2003, Hugang wrote:
Your script cannot work. Also, nothing hangs.
> Hello all: > > Steps to reproduce: > > rm -f /tmp/1.log > touch /tmp/1.log > echo << EOF > /tmp/hang.c ^^^^______ cat, not echo
> #include <sys/types.h> > #include <asm/fcntl.h> > > main() > { > int i; > char buf[1025]; > > i = open("/tmp/1.log", O_RDONLY | 040000, 0); > if ( i != -1) { > read(i, buf, 1); > } > printf("'%s'", buf); > } > EOF > gcc -o /tmp/hang /tmp/hang.c > /tmp/hang > >
This is a `strace` of it working:
getpid() = 14243 open("/tmp/1.log", O_RDONLY|0x4000) = 3 read(3, "", 1) = 0 fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(4, 1), ...}) = 0 old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x400aa000 ioctl(1, TCGETS, {B38400 opost isig icanon echo ...}) = 0 write(1, "\'\'", 2) = 2 munmap(0x400aa000, 4096) = 0 _exit(2) = ?
Cheers, Dick Johnson Penguin : Linux version 2.4.22 on an i686 machine (794.73 BogoMips). Note 96.31% of all statistics are fiction.
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