----- Original Message ----- > From: "Paul Woegerer" <[email protected]> > To: [email protected], "mathieu desnoyers" > <[email protected]>, "stefan seefeld" > <[email protected]> > Cc: [email protected] > Sent: Friday, February 14, 2014 8:45:05 AM > Subject: [PATCH] Force static_alloc setup to be written into memory > > 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 > > Signed-off-by: Paul Woegerer <[email protected]> > --- > liblttng-ust-libc-wrapper/lttng-ust-malloc.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/liblttng-ust-libc-wrapper/lttng-ust-malloc.c > b/liblttng-ust-libc-wrapper/lttng-ust-malloc.c > index 8296ae2..7dd647f 100644 > --- a/liblttng-ust-libc-wrapper/lttng-ust-malloc.c > +++ b/liblttng-ust-libc-wrapper/lttng-ust-malloc.c > @@ -198,6 +198,9 @@ void lookup_all_symbols(void) > */ > setup_static_allocator(); > > + /* Dlsym is defined pure -> force static alloc into memory */ > + cmm_barrier(); > + > /* Perform the actual lookups */ > af.calloc = dlsym(RTLD_NEXT, "calloc"); > af.malloc = dlsym(RTLD_NEXT, "malloc"); > @@ -207,7 +210,7 @@ void lookup_all_symbols(void) > af.posix_memalign = dlsym(RTLD_NEXT, "posix_memalign");
Shouldn't we also add a cmm_barrier() between the last call to dlsym() and the stores to cur_alloc then, to ensure that the allocator is swapped only after all calls to dlsym ? Thanks, Mathieu > > /* Populate the new allocator functions */ > - memcpy(&cur_alloc, &af, sizeof(cur_alloc)); > + cur_alloc = af; > } > > void *malloc(size_t size) > -- > 1.8.5.2 > > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
