Thanks for all of the help, and thanks for the patch Chris! I was hoping to submit a patch this weekend, so you just gave me back some time :) Alan
On Thu, Oct 15, 2020 at 2:08 AM Chris Johns <chr...@rtems.org> wrote: > > On 13/10/20 4:13 am, Joel Sherrill wrote: > > On Mon, Oct 12, 2020 at 11:15 AM Alan Cudmore <alan.cudm...@gmail.com > > <mailto:alan.cudm...@gmail.com>> wrote: > > > > Hi Chris, > > I'm not sure that I can easily create a test to show that this > > condition exists. I think the rtems_rfs_bitmap_create_search function > > works as it is intended to, but during the last iteration of the for > > loop, if 'size' is zero and 'bit' is 31, the 'search_map' variable is > > incremented once more, and the value of RTEMS_RFS_BITMAP_ELEMENT_CLEAR > > (0xFFFFFFFF) is written to that location. This location is one address > > beyond the memory that was allocated for the search_map in > > rtems_rfs_bitmap_open. > > I guess that most of the time this is a silent side effect, but my > > application just happened to have memory lined up such that the extra > > write causes the malloc Allocator mutex to fail, causing the > > malloc_info call to block indefinitely. I would consider this a lucky > > break! > > The exact same example application does not fail on RTEMS 4.11. I > > think the problem still exists, but in that case, the word that gets > > written is different. > > > > Here are some debug printfs from rtems_rfs_bitmap_open and > > rtems_rfs_bitmap_create_search: > > > > From rtems_rfs_bitmap_open: > > RFS - rtems_rfs_bitmap_open - search_bits malloced size = 16 bytes > > RFS - rtems_rfs_bitmap_open - addr of search_bits = 0x00C03814 > > RFS -> size of search_map = 4 > > RFS -> control->size = 4095 > > > > From the subsequent call to rtems_rfs_bitmap_create_search: > > These printfs are in the if clause where bit == 31 (line 633) > > RFS --> search_map before increment addr 00C03814, size = 3071 > > RFS --> search_map after increment -> writing > > RTEMS_RFS_BITMAP_ELEMENT_CLEAR (-1) to addr 00C03818 > > RFS --> search_map before increment addr 00C03818, size = 2047 > > RFS --> search_map after increment -> writing > > RTEMS_RFS_BITMAP_ELEMENT_CLEAR (-1) to addr 00C0381C > > RFS --> search_map before increment addr 00C0381C, size = 1023 > > RFS --> search_map after increment -> writing > > RTEMS_RFS_BITMAP_ELEMENT_CLEAR (-1) to addr 00C03820 > > RFS --> search_map before increment addr 00C03820, size = 0 > > RFS --> search_map after increment -> writing > > RTEMS_RFS_BITMAP_ELEMENT_CLEAR (-1) to addr 00C03824 > > > > It's this last write to 00C03824 that causes the problem. I think the > > fix just involves checking to see if size == 0 before executing the if > > clause. I wanted to be sure that this extra write was not needed. > > > > If you have an idea for a test case, I can work on it, but if you > > think that this is good enough, I can propose a patch. > > > > Also, thanks for the idea of using RTEMS_DEBUG Sebastian, I need to > > upgrade my RTEMS toolbox with the latest techniques. > > > > > > If, while analysing this issues, you came up with any consistency checks > > or assertions that can be added to the code when debug is enabled, > > those would be welcomed. It is hard to go back and add them without > > the analysis like you did hunting this bug. > > I have added an _Assert (thanks Sebastian) and I now see: > > *** BEGIN OF TEST FSRFSBITMAP 1 *** > > *** TEST VERSION: 6.0.0.df9cc1aee87da6c6ba41d52454fa5f45fba74501 > > *** TEST STATE: EXPECTED_PASS > > *** TEST BUILD: RTEMS_DEBUG > > *** TEST TOOLS: 10.2.1 20200918 (RTEMS 6, RSB > ed5030bc24dbfdfac52074ed78cf4231bf1f353d, Newlib 749cbcc) > Initializing filesystem RFS > > assertion "search_map >= control->search_bits && search_map < > (control->search_bits + > rtems_rfs_bitmap_elements(rtems_rfs_bitmap_elements(control->size)))" failed: > file "../../../cpukit/libfs/src/rfs/rtems-rfs-bitmaps.c", line 648, function: > rtems_rfs_bitmap_create_search > > > > I have a patch to fix this I will post. > > Thank you Alan for the report and the analysis. It made my job nice and > simple. > > Chris _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel