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Fix crash in tracing object allocations

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ObjectSpace.trace_object_allocations_start could crash since it adds a
TracePoint for when objects are freed. However, TracePoint could crash
since it modifies st tables while inside the GC that is trying to free
the object. This could cause a memory allocation to happen which would
crash if it triggers another GC.

See a crash log: http://ci.rvm.jp/results/trunk@ruby-sp1/4373707
This commit is contained in:
Peter Zhu 2023-01-03 10:59:47 -05:00
parent 3bcf92d8af
commit b8a3f1bd45
Notes: git 2023-01-04 14:11:26 +00:00 
Merged: https://github.com/ruby/ruby/pull/7058
3 changed files with 10 additions and 2 deletions
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1
ext/objspace/depend
View File

@ -158,6 +158,7 @@ object_tracing.o: $(hdrdir)/ruby/missing.h
object_tracing.o: $(hdrdir)/ruby/ruby.h object_tracing.o: $(hdrdir)/ruby/ruby.h
object_tracing.o: $(hdrdir)/ruby/st.h object_tracing.o: $(hdrdir)/ruby/st.h
object_tracing.o: $(hdrdir)/ruby/subst.h object_tracing.o: $(hdrdir)/ruby/subst.h
object_tracing.o: $(top_srcdir)/gc.h
object_tracing.o: $(top_srcdir)/internal.h object_tracing.o: $(top_srcdir)/internal.h
object_tracing.o: object_tracing.c object_tracing.o: object_tracing.c
object_tracing.o: objspace.h object_tracing.o: objspace.h

7
ext/objspace/object_tracing.c
View File

@ -13,6 +13,7 @@
**********************************************************************/ **********************************************************************/
#include "gc.h"
#include "internal.h" #include "internal.h"
#include "ruby/debug.h" #include "ruby/debug.h"
#include "objspace.h" #include "objspace.h"
@ -121,6 +122,10 @@ freeobj_i(VALUE tpval, void *data)
st_data_t v; st_data_t v;
struct allocation_info *info; struct allocation_info *info;
/* Modifying the st table can cause allocations, which can trigger GC.
* Since freeobj_i is called during GC, it must not trigger another GC. */
VALUE gc_disabled = rb_gc_disable_no_rest();
if (arg->keep_remains) { if (arg->keep_remains) {
if (st_lookup(arg->object_table, obj, &v)) { if (st_lookup(arg->object_table, obj, &v)) {
info = (struct allocation_info *)v; info = (struct allocation_info *)v;
@ -135,6 +140,8 @@ freeobj_i(VALUE tpval, void *data)
ruby_xfree(info); ruby_xfree(info);
} }
} }
if (gc_disabled == Qfalse) rb_gc_enable();
} }
static int static int

4
gc.h
View File

@ -116,8 +116,6 @@ int ruby_get_stack_grow_direction(volatile VALUE *addr);
const char *rb_obj_info(VALUE obj); const char *rb_obj_info(VALUE obj);
const char *rb_raw_obj_info(char *const buff, const size_t buff_size, VALUE obj); const char *rb_raw_obj_info(char *const buff, const size_t buff_size, VALUE obj);
VALUE rb_gc_disable_no_rest(void);
struct rb_thread_struct; struct rb_thread_struct;
size_t rb_size_pool_slot_size(unsigned char pool_id); size_t rb_size_pool_slot_size(unsigned char pool_id);
@ -142,6 +140,8 @@ void rb_objspace_each_objects_without_setup(
size_t rb_gc_obj_slot_size(VALUE obj); size_t rb_gc_obj_slot_size(VALUE obj);
VALUE rb_gc_disable_no_rest(void);
RUBY_SYMBOL_EXPORT_END RUBY_SYMBOL_EXPORT_END
#endif /* RUBY_GC_H */ #endif /* RUBY_GC_H */