git: kernel - pc64 - Fix pv_free() race and add assertions
dillon at crater.dragonflybsd.org
Sun Oct 6 16:42:06 PDT 2013
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date: Sun Oct 6 16:34:53 2013 -0700
kernel - pc64 - Fix pv_free() race and add assertions
* Continued work trying to fix the bad *ptep ... panics. Previous commits
did not do the job. It is still unknown whether this one completely fixes
* The pmap pv_entry API was allowing pv_entry's to be retained with 0 refs
and then doing a separate check for pv_pmap == NULL to determine if the
pv_entry could be freed or not. This resulted in a SMP race where multiple
threads could pv_free() the same pv_entry.
* Change the code to supply an addition ref for pv_pmap != NULL and use the
1->0 transition to deterministically conditionalize the pv_free().
* Change the shortcuts in pv_hold_try() and pv_drop() to use the new
* Add some additional assertions and a generation count to try to check bugs.
Summary of changes:
sys/platform/pc64/include/pmap.h | 2 +-
sys/platform/pc64/x86_64/pmap.c | 263 ++++++++++++++++++++++++++++++---------
sys/vm/vm_fault.c | 1 +
3 files changed, 204 insertions(+), 62 deletions(-)
DragonFly BSD source repository
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