Re: lib/57628: multithread programs may deadlock in ld.elf_so (sparc on sparc64)

[Martin Husemann <martin%duskware.de@localhost>]

The following reply was made to PR lib/57628; it has been noted by GNATS.

From: Martin Husemann <martin%duskware.de@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: lib/57628: multithread programs may deadlock in ld.elf_so (sparc
 on sparc64)
Date: Wed, 27 Sep 2023 20:05:11 +0200

 The attached patch seems to fix the issue for me, w/o any obivous bad
 side effects (ld.elf_so size ~the same, initial tests work fine).
 
 The same gdb test run from the previous rump example now shows both copies
 of __libc_atomic_init() being called - the ld.elf_so internal one very
 early (before any userland threads could have been created) and the second
 one when libc constructors are run.
 
 All our ld.elf_so seem to have the hidden function, but it is a no-op on most
 architectures (when hardware supported atomic ops are good enough), so no
 ifdef magic or whatever seems needed.
 
 Is it this simple? Am I overlooking something?
 Will run complete tests now...
 
 Martin
 
 Index: rtld.c
 ===================================================================
 RCS file: /cvsroot/src/libexec/ld.elf_so/rtld.c,v
 retrieving revision 1.215
 diff -u -p -r1.215 rtld.c
 --- rtld.c	30 Jul 2023 09:20:14 -0000	1.215
 +++ rtld.c	27 Sep 2023 17:52:04 -0000
 @@ -70,6 +70,13 @@ __RCSID("$NetBSD: rtld.c,v 1.215 2023/07
  #endif
  
  /*
 + * Hidden function from common/lib/libc/atomic - nop on machines
 + * with enough atomic ops. Need to explicitly call it early.
 + * libc has the same symbol and will initialize itself, but not our copy.
 + */
 +void __libc_atomic_init(void);
 +
 +/*
   * Function declarations.
   */
  static void     _rtld_init(caddr_t, caddr_t, const char *);
 @@ -404,6 +411,8 @@ _rtld_init(caddr_t mapbase, caddr_t relo
  	ehdr = (Elf_Ehdr *)mapbase;
  	_rtld_objself.phdr = (Elf_Phdr *)((char *)mapbase + ehdr->e_phoff);
  	_rtld_objself.phsize = ehdr->e_phnum * sizeof(_rtld_objself.phdr[0]);
 +
 +	__libc_atomic_init();
  }
  
  /*