POSIX FIFO/pipe

[Wei Shen]

Hi Joel,

I wrote several mails to you but got no reply for quite a few days. I guess
there must be sth. wrong. Maybe, my mails were recognized as spams, so I try
adding rtems-users...

On 7/26/08, Wei Shen <cquark at gmail.com> wrote:

 Thanks for the quick reply.

On 7/25/08, Joel Sherrill <joel.sherrill at oarcorp.com> wrote:

> 1. POSIX says when pipe IO can be interrupted by signals. I remember we
>> think it is better to make FIFO/pipe independant of POSIX API.
>>
> What is your blocking mechanism in the pipe code?
> When blocking in RTEMS, you can specify an extra state bit
> STATES_INTERRUPTIBLE_BY_SIGNAL.  So you can be blocking
> on a mutex and that particular mutex API implementation may be
> written to set the STATES_INTERRUPTIBLE_BY_SIGNAL bit.
> When a signal occurs, that bit is checked.


I use semaphore and barrier. I just want barrier_wait to be interruptible,
but semaphore not.
I do not quite understand what you mean. I do not find such interfaces in
barrier implementation. Do you mean I just need to set
STATES_INTERRUPTIBLE_BY_SIGNAL before barrier_wait and clear it after; or
barrier need hooking to check the state bit?


> 3. For anonymous pipes, it is easier to implement them as FIFOs with
>> arbitrary names. So what kind of paths is prefered for pipes?
>
>
Maybe, sth. like: /tmp/.pipe#id, where id is a 32bit integer?


> BTW, I also found IMFS_memfile_write does not strictly follow POSIX in
>> that, it updates file ATime and MTime, while POSIX requires file write to
>> update MTime and CTime.
>>
>>
> Can you submit a patch and pointer to opengroup.org?


http://www.opengroup.org/onlinepubs/009695399/functions/write.html
"Upon successful completion, where *nbyte* is greater than 0, *write*()
shall mark for update the *st_ctime* and *st_mtime* fields of the file, and
if the file is a regular file, the S_ISUID and S_ISGID bits of the file mode
may be cleared."
(I have not checked the last sentence)

--- imfs.h.new  2008-07-25 14:20:27.000000000 -0700
+++ imfs.h      2008-07-09 23:03:51.000000000 -0700
@@ -196,12 +196,12 @@
     _jnode->stat_ctime  = (time_t) tv.tv_sec; \
   } while (0)

-#define IMFS_mtime_ctime_update( _jnode )   \
+#define IMFS_atime_mtime_update( _jnode )   \
   do {                                      \
     struct timeval tv;                      \
     gettimeofday( &tv, 0 );                 \
     _jnode->stat_mtime  = (time_t) tv.tv_sec; \
-    _jnode->stat_ctime  = (time_t) tv.tv_sec; \
+    _jnode->stat_atime  = (time_t) tv.tv_sec; \
   } while (0)

--- memfile.c.new       2008-07-25 14:19:38.000000000 -0700
+++ memfile.c   2008-07-02 18:37:38.000000000 -0700
@@ -844,7 +844,7 @@
     copied += to_copy;
   }

-  IMFS_mtime_ctime_update( the_jnode );
+  IMFS_atime_mtime_update( the_jnode );

   return copied;
 }
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