hrev53072 adds 1 changeset to branch 'master'
old head: 716ccf0492610e4d9e4c9325626b6b217db5b462
new head: 351575e0e432ad8ff46fc1e80a0b7f8eedf740bf
overview:
https://git.haiku-os.org/haiku/log/?qt=range&q=351575e0e432+%5E716ccf049261
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351575e0e432: kernel/vm: Do not invoke the low_resource monitor in
map_backing_store.
As the comment implies, we don't want to wait here, but low_resource()
waits forever when timeout=0. It doesn't seem to do anything with the
"size" argument at all, so not calling it is just as effective, and so
replace the comment there altogether.
The case where this was most often hit, causing a full system deadlock
in anything relating to memory management, was when the passed "size"
was 0. So now we check for this case explicity at the beginning and
panic() on KDEBUG kernels for it.
[ Augustin Cavalier <waddlesplash@xxxxxxxxx> ]
----------------------------------------------------------------------------
Revision: hrev53072
Commit: 351575e0e432ad8ff46fc1e80a0b7f8eedf740bf
URL: https://git.haiku-os.org/haiku/commit/?id=351575e0e432
Author: Augustin Cavalier <waddlesplash@xxxxxxxxx>
Date: Mon Apr 15 15:14:59 2019 UTC
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1 file changed, 13 insertions(+), 5 deletions(-)
src/system/kernel/vm/vm.cpp | 18 +++++++++++++-----
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diff --git a/src/system/kernel/vm/vm.cpp b/src/system/kernel/vm/vm.cpp
index 04c6980598..920745c4b5 100644
--- a/src/system/kernel/vm/vm.cpp
+++ b/src/system/kernel/vm/vm.cpp
@@ -805,6 +805,14 @@ map_backing_store(VMAddressSpace* addressSpace, VMCache*
cache, off_t offset,
_area, areaName));
cache->AssertLocked();
+ if (size == 0) {
+#if KDEBUG
+ panic("map_backing_store(): called with size=0 for area '%s'!",
+ areaName);
+#endif
+ return B_BAD_VALUE;
+ }
+
uint32 allocationFlags = HEAP_DONT_WAIT_FOR_MEMORY
| HEAP_DONT_LOCK_KERNEL_SPACE;
int priority;
@@ -873,11 +881,11 @@ map_backing_store(VMAddressSpace* addressSpace, VMCache*
cache, off_t offset,
allocationFlags, _virtualAddress);
if (status == B_NO_MEMORY
&& addressRestrictions->address_specification ==
B_ANY_KERNEL_ADDRESS) {
- // Since the kernel address space is locked by the caller, we
can't
- // wait here as of course no resources can be released while
the locks
- // are held. But we can at least issue this so the next caller
doesn't
- // run into the same problem.
- low_resource(B_KERNEL_RESOURCE_ADDRESS_SPACE, size, 0, 0);
+ // TODO: At present, there is no way to notify the low_resource
monitor
+ // that kernel addresss space is fragmented, nor does it check
for this
+ // automatically. Due to how many locks are held, we cannot
wait here
+ // for space to be freed up, but it would be good to at least
notify
+ // that we tried and failed to allocate some amount.
}
if (status != B_OK)
goto err2;
