nuttx-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From GitBox <...@apache.org>
Subject [GitHub] [incubator-nuttx] patacongo opened a new issue #1108: Remove streams from Kernel Threads
Date Sat, 23 May 2020 14:27:34 GMT

patacongo opened a new issue #1108:
URL: https://github.com/apache/incubator-nuttx/issues/1108


   ## No Streams in Kernel Threads
   
   Kernel threads are not permitted to use the C library buffer I/O, "stream", interfaces.
 Those are interfaces like fopen, fread, fwrite, fclose, etc.  Those are strictly for use
by user applications.  This is because these functions modify errno variables and create cancellation
points and perhaps other things that are undesirable within the OS.
   
   The thread create logic is largely the same for both kernel threads and for application
threads:  They both allocate a large buffer from the user memory pool for the stream `FILE`
array.  Since kernel threads this is a waste of memory since the kernel threads should not
be using streams.
   
   ## Remove Kernel Thread Stream Allocation
   
   The proposal is (1) Verify that there is no use of streams within the OS, (2) remove the
stream allocation for kernel threads, and (3) assure that there are proper checks in place
so that there are no uses of the NULL stream array pointer.
   
   For the most part, the OS is clean, there are essentially no use of streams within the
OS.  There are, however, a few violations of this that will need to be fixed; fopen() is called
in some of the lc3850.
   
   ## Remove the File Descriptor Array Too
   
   A second phase would be to remove the file descriptor array from kernel threads.  File
descriptors are, again, only for use by applications; within the OS, file access is done using
the struct file (aka, FILE), structure directly.  However, I suspect that there are many hidden
uses of file descriptors in the system.  For one, file_open() which opens the detached file,
is not fully implemented; it cheats and uses file descriptors.  So let's consider removal
of the file descriptor allocation as a second step after the stream allocations have been
removed.


----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

For queries about this service, please contact Infrastructure at:
users@infra.apache.org



Mime
View raw message