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6782457: CMS: Livelock in CompactibleFreeListSpace::block_size()

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6736295: SIGSEGV in product jvm, assertion "these are the only valid states during a mark sweep" in fastdebug

Restructured the code in the perm gen allocation retry loop so as to avoid "safepoint-blocking" on locks, in this case the Heap_lock, while holding uninitialized allocated heap storage.

Reviewed-by: apetrusenko, iveresov, jcoomes, jmasa, poonam
This commit is contained in:
Y. Srinivas Ramakrishna 2008-12-10 23:46:10 -08:00
parent dd80e77a74
commit 26f6b1692a
1 changed files with 32 additions and 32 deletions
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26
hotspot/src/share/vm/memory/permGen.cpp
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@ -26,20 +26,24 @@
#include "incls/_permGen.cpp.incl"
HeapWord* PermGen::mem_allocate_in_gen(size_t size, Generation* gen) {
MutexLocker ml(Heap_lock);
GCCause::Cause next_cause = GCCause::_permanent_generation_full;
GCCause::Cause prev_cause = GCCause::_no_gc;
unsigned int gc_count_before, full_gc_count_before;
HeapWord* obj;
for (;;) {
HeapWord* obj = gen->allocate(size, false);
if (obj != NULL) {
{
MutexLocker ml(Heap_lock);
if ((obj = gen->allocate(size, false)) != NULL) {
return obj;
}
if (gen->capacity() < _capacity_expansion_limit ||
prev_cause != GCCause::_no_gc) {
obj = gen->expand_and_allocate(size, false);
}
if (obj == NULL && prev_cause != GCCause::_last_ditch_collection) {
if (obj != NULL || prev_cause == GCCause::_last_ditch_collection) {
return obj;
}
if (GC_locker::is_active_and_needs_gc()) {
// If this thread is not in a jni critical section, we stall
// the requestor until the critical section has cleared and
@ -61,12 +65,12 @@ HeapWord* PermGen::mem_allocate_in_gen(size_t size, Generation* gen) {
return NULL;
}
}
// Read the GC count while holding the Heap_lock
unsigned int gc_count_before = SharedHeap::heap()->total_collections();
unsigned int full_gc_count_before = SharedHeap::heap()->total_full_collections();
{
MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back
gc_count_before = SharedHeap::heap()->total_collections();
full_gc_count_before = SharedHeap::heap()->total_full_collections();
}
// Give up heap lock above, VMThread::execute below gets it back
VM_GenCollectForPermanentAllocation op(size, gc_count_before, full_gc_count_before,
next_cause);
VMThread::execute(&op);
@ -80,12 +84,8 @@ HeapWord* PermGen::mem_allocate_in_gen(size_t size, Generation* gen) {
if (obj != NULL) {
return obj;
}
}
prev_cause = next_cause;
next_cause = GCCause::_last_ditch_collection;
} else {
return obj;
}
}
}