From mboxrd@z Thu Jan 1 00:00:00 1970 From: amonakov@ispras.ru (Alexander Monakov) Date: Fri, 14 Feb 2014 18:23:19 +0400 (MSK) Subject: [lttng-dev] [PATCH] Force static_alloc setup to be written into memory In-Reply-To: <1392385505-13405-1-git-send-email-paul_woegerer@mentor.com> References: <1392385505-13405-1-git-send-email-paul_woegerer@mentor.com> Message-ID: On Fri, 14 Feb 2014, Paul Woegerer wrote: > As explained by Alexander Monakov, dlsym() is defined to be pure, thus the > compiler is allowed to assume that there is no need to write the changes > performed by setup_static_allocator() into memory prior to calling dlsym(). > The added cmm_barrier() forces the compiler to write the changes into memory. > > For more details refer to: > http://lists.lttng.org/pipermail/lttng-dev/2014-February/022389.html If everyone here agrees that this is a workaround for a glibc bug, please add a note to that effect in the patch and please notify glibc upstream (again). FWIW, when toying with a similar code I implemented a different workaround along the lines of #define dlsym glibc_dlsym_proto_lies_about_leafness #include #undef dlsym extern void *dlsym(void *, const char *); Thus avoiding the need to sprinkle unneeded compiler memory barriers in code. HTH Alexander