Module Name: src
Committed By: thorpej
Date: Sun May 23 19:13:27 UTC 2021
Modified Files:
src/sys/arch/alpha/alpha: pmap.c
Log Message:
Fix a bug in pmap_tlb_shootdown_all_user(), where it was not
stashing away the pointer to the pmap in the TLB context structure
like pmap_tlb_shootdown() was doing. This would result in the
following failure scenario:
- Page fault handler calls pmap_enter() to map a page. Mapping
is the first one for that L2 PT L3 PT, meaning that an L2 PT
and an L3 PT must be allocated.
- L2 PT allocation succeeds.
- L3 PT allocation fails under memory pressure.
- pmap_enter() goes to drop the reference on the L2 PT, which, because
it was the first of its mappings, frees the L2 PT. Becuse PALcode
may have already tried to service a TLB miss though that L2 PT, we
must issue an all-user-VA shootdown, and call pmap_tlb_shootdown_all_user()
to do so.
- pmap_tlb_shootnow() is called and an assert fires because the TLB
context structure does not point to a pmap.
This did not fail in the pmap_remove() scenario because the TLB context
would have already had at least one call to pmap_tlb_shootdown(), which
was initializing the pmap pointer properly.
PR port-alpha/56200
To generate a diff of this commit:
cvs rdiff -u -r1.276 -r1.277 src/sys/arch/alpha/alpha/pmap.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
