Hi, We had a similar issue, I believe FD_SETSIZE is only defined to 64 if it's not already defined by the application, see (select.h), you would probably have to pass -DFD_SETSIZE=500 from the complier command line though as you would need to set the definition really early before most includes.
On Wed, 21 Nov 2018, 04:21 Ian Caddy <i...@goanna.iinet.net.au wrote: > Hi All, > > We are in the process of porting an existing application from RTEMS4.10 > to RTEMS5, and have an issue with "select". > > We have previously known of the issue which also exists in RTEMS 4.10, > but the problem is exacerbated in RTEMS5 due to the change in the way > the libio descriptors are allocated. > > First some history. With RTEMS and newlib and "select" this only works > for the first 64 file descriptors as the fd_set size is set in newlib, > by default to a size of 64. Therefore you can not use the select call > is your file descriptor is greater than 64 (on RTEMS 4.10 we got around > this by creating our own select with our own fd_set), but on RTEMS 5 we > have also moved to libbsd with a brand new select and underlying > implementation. > > We also open quite a lot of files at particular times, so our > CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS is set to 500. These files are > open at a different time to using the select, and so they lived together > OK. > > With RTEMS 4.10 the libio would allocate off the list and once freed > they would be returned to the free list. The opens would allocate from > the start of the list, so mostly the fd's were low numbers (under 64). > > With RTEMS 5, this has changed so when freed the descriptors are now put > at the end of the free list, which means we will use all the libio > allocators before wrapping around into which ever order they were freed > previously. > > This means our select is currently pretty much guaranteed going over the > default 64 fd_set limit at some stage (currently it is happening right > at the beginning.... for now on my simple system I have changed our > MAX_FILE_DESCRIPTORS to 64 and the select is working OK. > > Does anyone know of a nice way around this issue without saying don't > use select.... ;-) > > regards, > > Ian Caddy > > > _______________________________________________ > users mailing list > users@rtems.org > http://lists.rtems.org/mailman/listinfo/users
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