On 2/11/17 5:04 PM, Graham Northup wrote: > Bash Version: 4.4 > Patch Level: 11 > Release Status: release > > Description: > > I'm getting a mysterious hang on one of our Arch Linux machines for a > particular, rather simple script; getting a debugger attached to the > process after building some debugging symbols, I tracked the hang down > to this loop in bgp_delete (with some minor formatting):
It seems obvious in retrospect that the cause is in bgp_add, where there's
no check for the hashed pid colliding with the index into the pidstat list.
Here's a patch that avoids that issue and catches the symptom you found in
case the cause is something else.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU c...@case.edu http://cnswww.cns.cwru.edu/~chet/
*** ../bash-4.4-patched/jobs.c 2016-11-11 14:06:24.000000000 -0500
--- jobs.c 2017-02-16 11:07:13.000000000 -0500
***************
*** 815,818 ****
--- 798,812 ----
bucket = pshash_getbucket (pid);
psi = bgp_getindex ();
+
+ /* XXX - what if psi == *bucket? */
+ if (psi == *bucket)
+ {
+ #ifdef DEBUG
+ internal_warning ("hashed pid %d (pid %d) collides with bgpids.head, skipping", psi, pid);
+ #endif
+ bgpids.storage[psi].pid = NO_PID; /* make sure */
+ psi = bgp_getindex (); /* skip to next one */
+ }
+
ps = &bgpids.storage[psi];
***************
*** 866,871 ****
/* Search chain using hash to find bucket in pidstat_table */
for (psi = *(pshash_getbucket (pid)); psi != NO_PIDSTAT; psi = bgpids.storage[psi].bucket_next)
! if (bgpids.storage[psi].pid == pid)
! break;
if (psi == NO_PIDSTAT)
--- 860,872 ----
/* Search chain using hash to find bucket in pidstat_table */
for (psi = *(pshash_getbucket (pid)); psi != NO_PIDSTAT; psi = bgpids.storage[psi].bucket_next)
! {
! if (bgpids.storage[psi].pid == pid)
! break;
! if (psi == bgpids.storage[psi].bucket_next) /* catch reported bug */
! {
! internal_warning ("bgp_delete: BUG: psi (%d) == storage[psi].bucket_next", psi);
! return 0;
! }
! }
if (psi == NO_PIDSTAT)
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