• istruewing@chilla.local's avatar
    Bug#25460 - High concurrency MyISAM access causes severe mysqld crash. · 67d97254
    istruewing@chilla.local authored
    The previous two patches for this bug worked together so that
    no permanent table was memory mapped. The first patch tried to
    avoid mapping while a table is in use. It allowed mapping only
    if there was exactly one lock on the table, assuming that the
    calling thread owned it. During mi_open(), a different call to
    memory mapping was coded, which did not have this limitation.
    
    The second patch tried to remove the code duplication and just
    called mi_extra() from mi_open() an thus inherited the limitation.
    But on open, a thread does not have a lock on the table...
    
    A possible solution would be to check for zero or one lock.
    But since I learned that it is safe to memory map a file while
    normal file I/O is done on it, I removed the restriction altogether
    and allow to memory map while a table is in use.
    
    No test case. I do not see a chance to verify with the test suite
    which kind of I/O is used on a table.
    67d97254
mi_extra.c 13.3 KB