From eb92159d72fc711387f7e17ffbaca1678f23fd47 Mon Sep 17 00:00:00 2001 From: 卜部昌平 Date: Thu, 3 Oct 2019 12:26:41 +0900 Subject: Revert https://github.com/ruby/ruby/pull/2486 This reverts commits: 10d6a3aca7 8ba48c1b85 fba8627dc1 dd883de5ba 6c6a25feca 167e6b48f1 7cb96d41a5 3207979278 595b3c4fdd 1521f7cf89 c11c5e69ac cf33608203 3632a812c0 f56506be0d 86427a3219 . The reason for the revert is that we observe ABA problem around inline method cache. When a cache misshits, we search for a method entry. And if the entry is identical to what was cached before, we reuse the cache. But the commits we are reverting here introduced situations where a method entry is freed, then the identical memory region is used for another method entry. An inline method cache cannot detect that ABA. Here is a code that reproduce such situation: ```ruby require 'prime' class << Integer alias org_sqrt sqrt def sqrt(n) raise end GC.stress = true Prime.each(7*37){} rescue nil # <- Here we populate CC class << Object.new; end # These adjacent remove-then-alias maneuver # frees a method entry, then immediately # reuses it for another. remove_method :sqrt alias sqrt org_sqrt end Prime.each(7*37).to_a # <- SEGV ``` --- internal.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'internal.h') diff --git a/internal.h b/internal.h index dee7775d95..2346703d68 100644 --- a/internal.h +++ b/internal.h @@ -2330,6 +2330,7 @@ enum method_missing_reason { MISSING_NONE = 0x40 }; struct rb_callable_method_entry_struct; +struct rb_method_definition_struct; struct rb_execution_context_struct; struct rb_control_frame_struct; struct rb_calling_info; @@ -2341,6 +2342,7 @@ struct rb_call_cache { /* inline cache: values */ const struct rb_callable_method_entry_struct *me; + const struct rb_method_definition_struct *def; VALUE (*call)(struct rb_execution_context_struct *ec, struct rb_control_frame_struct *cfp, -- cgit v1.2.3