• Thomas Munro's avatar
    Fix race in dsm_unpin_segment() when handles are reused. · 0b55aaac
    Thomas Munro authored
    Teach dsm_unpin_segment() to skip segments that are in the process
    of being destroyed by another backend, when searching for a handle.
    Such a segment cannot possibly be the one we are looking for, even
    if its handle matches.  Another slot might hold a recently created
    segment that has the same handle value by coincidence, and we need
    to keep searching for that one.
    
    The bug caused rare "cannot unpin a segment that is not pinned"
    errors on 10 and 11.  Similar to commit 6c0fb941 for dsm_attach().
    
    Back-patch to 10, where dsm_unpin_segment() landed.
    
    Author: Thomas Munro
    Reported-by: Justin Pryzby
    Tested-by: Justin Pryzby (along with other recent DSA/DSM fixes)
    Discussion: https://postgr.es/m/20190216023854.GF30291@telsasoft.com
    0b55aaac
dsm.c 33.9 KB