On Thu, Oct 15, 2020, 7:15 AM Alan Cudmore <alan.cudm...@gmail.com> wrote:
> 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 :) > Glad you found this! The RFS was new in 4.10 as I recall. You guys have missions using this. Do you need to locally fix this? It also needs to be fixed in 4.11. For posterity, if a fix is needed for 4.10, should we push it even though we have no plans for a future release from that branch? Just asking since a small number of other patches have been pushed to that branch. 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 >
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