From c94e3311ecf51bf3c6017ab4028debcae2a5dd6e Mon Sep 17 00:00:00 2001 From: Eli Zaretskii Date: Sat, 24 May 2014 15:02:25 +0300 Subject: [PATCH] Avoid marking too deep portions of stack in mark_stack. src/alloc.c (garbage_collect_1): New function, with all of the guts of Fgarbage_collect. (mark_stack): Accept an argument END and don't mark Lisp objects on the stack beyond the address given by END. Calculation of END was moved to Fgarbage_collect. (Fgarbage_collect): Calculate the end address of the stack portion that needs to be examined by mark_stack, and pass that address to garbage_collect_1, which will pass it to mark_stack. See http://lists.gnu.org/archive/html/emacs-devel/2014-05/msg00270.html for more details about the underlying problems. In particular, this avoids dumping Emacs with the large hash-table whose value is held in purify-flag for most of the time loadup.el runs. --- src/ChangeLog | 15 +++++ src/alloc.c | 160 +++++++++++++++++++++++++++----------------------- 2 files changed, 103 insertions(+), 72 deletions(-) diff --git a/src/ChangeLog b/src/ChangeLog index 7f83681e0a..19da2bf89f 100644 --- a/src/ChangeLog +++ b/src/ChangeLog @@ -1,3 +1,18 @@ +2014-05-24 Eli Zaretskii + + * alloc.c (garbage_collect_1): New function, with all of the guts + of Fgarbage_collect. + (mark_stack): Accept an argument END and don't mark Lisp objects + on the stack beyond the address given by END. Calculation of END + was moved to Fgarbage_collect. + (Fgarbage_collect): Calculate the end address of the stack portion + that needs to be examined by mark_stack, and pass that address to + garbage_collect_1, which will pass it to mark_stack. See + http://lists.gnu.org/archive/html/emacs-devel/2014-05/msg00270.html + for more details about the underlying problems. In particular, + this avoids dumping Emacs with the large hash-table whose value is + held in purify-flag for most of the time loadup.el runs. + 2014-05-24 Jan Djärv * xfns.c (x_window_property_intern): New function (code from diff --git a/src/alloc.c b/src/alloc.c index 1dc33b7252..d221cc7e96 100644 --- a/src/alloc.c +++ b/src/alloc.c @@ -4876,61 +4876,8 @@ dump_zombies (void) from the stack start. */ static void -mark_stack (void) +mark_stack (void *end) { - void *end; - -#ifdef HAVE___BUILTIN_UNWIND_INIT - /* Force callee-saved registers and register windows onto the stack. - This is the preferred method if available, obviating the need for - machine dependent methods. */ - __builtin_unwind_init (); - end = &end; -#else /* not HAVE___BUILTIN_UNWIND_INIT */ -#ifndef GC_SAVE_REGISTERS_ON_STACK - /* jmp_buf may not be aligned enough on darwin-ppc64 */ - union aligned_jmpbuf { - Lisp_Object o; - sys_jmp_buf j; - } j; - volatile bool stack_grows_down_p = (char *) &j > (char *) stack_base; -#endif - /* This trick flushes the register windows so that all the state of - the process is contained in the stack. */ - /* Fixme: Code in the Boehm GC suggests flushing (with `flushrs') is - needed on ia64 too. See mach_dep.c, where it also says inline - assembler doesn't work with relevant proprietary compilers. */ -#ifdef __sparc__ -#if defined (__sparc64__) && defined (__FreeBSD__) - /* FreeBSD does not have a ta 3 handler. */ - asm ("flushw"); -#else - asm ("ta 3"); -#endif -#endif - - /* Save registers that we need to see on the stack. We need to see - registers used to hold register variables and registers used to - pass parameters. */ -#ifdef GC_SAVE_REGISTERS_ON_STACK - GC_SAVE_REGISTERS_ON_STACK (end); -#else /* not GC_SAVE_REGISTERS_ON_STACK */ - -#ifndef GC_SETJMP_WORKS /* If it hasn't been checked yet that - setjmp will definitely work, test it - and print a message with the result - of the test. */ - if (!setjmp_tested_p) - { - setjmp_tested_p = 1; - test_setjmp (); - } -#endif /* GC_SETJMP_WORKS */ - - sys_setjmp (j.j); - end = stack_grows_down_p ? (char *) &j + sizeof j : (char *) &j; -#endif /* not GC_SAVE_REGISTERS_ON_STACK */ -#endif /* not HAVE___BUILTIN_UNWIND_INIT */ /* This assumes that the stack is a contiguous region in memory. If that's not the case, something has to be done here to iterate @@ -5538,22 +5485,15 @@ mark_pinned_symbols (void) } } -DEFUN ("garbage-collect", Fgarbage_collect, Sgarbage_collect, 0, 0, "", - doc: /* Reclaim storage for Lisp objects no longer needed. -Garbage collection happens automatically if you cons more than -`gc-cons-threshold' bytes of Lisp data since previous garbage collection. -`garbage-collect' normally returns a list with info on amount of space in use, -where each entry has the form (NAME SIZE USED FREE), where: -- NAME is a symbol describing the kind of objects this entry represents, -- SIZE is the number of bytes used by each one, -- USED is the number of those objects that were found live in the heap, -- FREE is the number of those objects that are not live but that Emacs - keeps around for future allocations (maybe because it does not know how - to return them to the OS). -However, if there was overflow in pure space, `garbage-collect' -returns nil, because real GC can't be done. -See Info node `(elisp)Garbage Collection'. */) - (void) +/* Subroutine of Fgarbage_collect that does most of the work. It is a + separate function so that we could limit mark_stack in searching + the stack frames below this function, thus avoiding the rare cases + where mark_stack finds values that look like live Lisp objects on + portions of stack that couldn't possibly contain such live objects. + For more details of this, see the discussion at + http://lists.gnu.org/archive/html/emacs-devel/2014-05/msg00270.html. */ +static Lisp_Object +garbage_collect_1 (void *end) { struct buffer *nextb; char stack_top_variable; @@ -5651,7 +5591,7 @@ See Info node `(elisp)Garbage Collection'. */) #if (GC_MARK_STACK == GC_MAKE_GCPROS_NOOPS \ || GC_MARK_STACK == GC_MARK_STACK_CHECK_GCPROS) - mark_stack (); + mark_stack (end); #else { register struct gcpro *tail; @@ -5674,7 +5614,7 @@ See Info node `(elisp)Garbage Collection'. */) #endif #if GC_MARK_STACK == GC_USE_GCPROS_CHECK_ZOMBIES - mark_stack (); + mark_stack (end); #endif /* Everything is now marked, except for the data in font caches @@ -5834,6 +5774,82 @@ See Info node `(elisp)Garbage Collection'. */) return retval; } +DEFUN ("garbage-collect", Fgarbage_collect, Sgarbage_collect, 0, 0, "", + doc: /* Reclaim storage for Lisp objects no longer needed. +Garbage collection happens automatically if you cons more than +`gc-cons-threshold' bytes of Lisp data since previous garbage collection. +`garbage-collect' normally returns a list with info on amount of space in use, +where each entry has the form (NAME SIZE USED FREE), where: +- NAME is a symbol describing the kind of objects this entry represents, +- SIZE is the number of bytes used by each one, +- USED is the number of those objects that were found live in the heap, +- FREE is the number of those objects that are not live but that Emacs + keeps around for future allocations (maybe because it does not know how + to return them to the OS). +However, if there was overflow in pure space, `garbage-collect' +returns nil, because real GC can't be done. +See Info node `(elisp)Garbage Collection'. */) + (void) +{ +#if (GC_MARK_STACK == GC_MAKE_GCPROS_NOOPS \ + || GC_MARK_STACK == GC_MARK_STACK_CHECK_GCPROS \ + || GC_MARK_STACK == GC_USE_GCPROS_CHECK_ZOMBIES) + void *end; + +#ifdef HAVE___BUILTIN_UNWIND_INIT + /* Force callee-saved registers and register windows onto the stack. + This is the preferred method if available, obviating the need for + machine dependent methods. */ + __builtin_unwind_init (); + end = &end; +#else /* not HAVE___BUILTIN_UNWIND_INIT */ +#ifndef GC_SAVE_REGISTERS_ON_STACK + /* jmp_buf may not be aligned enough on darwin-ppc64 */ + union aligned_jmpbuf { + Lisp_Object o; + sys_jmp_buf j; + } j; + volatile bool stack_grows_down_p = (char *) &j > (char *) stack_base; +#endif + /* This trick flushes the register windows so that all the state of + the process is contained in the stack. */ + /* Fixme: Code in the Boehm GC suggests flushing (with `flushrs') is + needed on ia64 too. See mach_dep.c, where it also says inline + assembler doesn't work with relevant proprietary compilers. */ +#ifdef __sparc__ +#if defined (__sparc64__) && defined (__FreeBSD__) + /* FreeBSD does not have a ta 3 handler. */ + asm ("flushw"); +#else + asm ("ta 3"); +#endif +#endif + + /* Save registers that we need to see on the stack. We need to see + registers used to hold register variables and registers used to + pass parameters. */ +#ifdef GC_SAVE_REGISTERS_ON_STACK + GC_SAVE_REGISTERS_ON_STACK (end); +#else /* not GC_SAVE_REGISTERS_ON_STACK */ + +#ifndef GC_SETJMP_WORKS /* If it hasn't been checked yet that + setjmp will definitely work, test it + and print a message with the result + of the test. */ + if (!setjmp_tested_p) + { + setjmp_tested_p = 1; + test_setjmp (); + } +#endif /* GC_SETJMP_WORKS */ + + sys_setjmp (j.j); + end = stack_grows_down_p ? (char *) &j + sizeof j : (char *) &j; +#endif /* not GC_SAVE_REGISTERS_ON_STACK */ +#endif /* not HAVE___BUILTIN_UNWIND_INIT */ +#endif /* GC_MARK_STACK */ + return garbage_collect_1 (end); +} /* Mark Lisp objects in glyph matrix MATRIX. Currently the only interesting objects referenced from glyphs are strings. */ -- 2.20.1