On Mon, Jun 20, 2022 at 12:20 PM Martin Liška <mli...@suse.cz> wrote:
>
> On 6/20/22 11:32, Richard Biener wrote:
> > On Thu, Jun 16, 2022 at 9:01 AM Martin Liška <mli...@suse.cz> wrote:
> >>
> >> lto-plugin/ChangeLog:
> >>
> >> * lto-plugin.c (plugin_lock): New lock.
> >> (claim_file_handler): Use mutex for critical section.
> >> (onload): Initialize mutex.
> >> ---
> >> lto-plugin/lto-plugin.c | 16 +++++++++++++++-
> >> 1 file changed, 15 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/lto-plugin/lto-plugin.c b/lto-plugin/lto-plugin.c
> >> index 00b760636dc..13118c4983c 100644
> >> --- a/lto-plugin/lto-plugin.c
> >> +++ b/lto-plugin/lto-plugin.c
> >> @@ -55,6 +55,7 @@ along with this program; see the file COPYING3. If not
> >> see
> >> #include <unistd.h>
> >> #include <fcntl.h>
> >> #include <sys/types.h>
> >> +#include <pthread.h>
> >
> > Not sure if we support any non-pthread target for building the LTO
> > plugin, but it
> > seems we have
> >
> > # Among non-ELF, only Windows platforms support the lto-plugin so far.
> > # Build it unless LTO was explicitly disabled.
> > case $target in
> > *-cygwin* | *-mingw*) build_lto_plugin=$enable_lto ;;
> >
> > which suggests that at least build validating the above with --enable-lto
>
> Verified that it's fine.
>
> >
> > IIRC we have gthr-*.h in libgcc/, not sure if that's usable in a
> > host linker plugin.
> >
> >> #ifdef HAVE_SYS_WAIT_H
> >> #include <sys/wait.h>
> >> #endif
> >> @@ -157,6 +158,9 @@ enum symbol_style
> >> ss_uscore, /* Underscore prefix all symbols. */
> >> };
> >>
> >> +/* Plug-in mutex. */
> >> +static pthread_mutex_t plugin_lock;
> >> +
> >> static char *arguments_file_name;
> >> static ld_plugin_register_claim_file register_claim_file;
> >> static ld_plugin_register_all_symbols_read register_all_symbols_read;
> >> @@ -1262,15 +1266,18 @@ claim_file_handler (const struct
> >> ld_plugin_input_file *file, int *claimed)
> >> lto_file.symtab.syms);
> >> check (status == LDPS_OK, LDPL_FATAL, "could not add symbols");
> >>
> >> + pthread_mutex_lock (&plugin_lock);
> >> num_claimed_files++;
> >> claimed_files =
> >> xrealloc (claimed_files,
> >> num_claimed_files * sizeof (struct plugin_file_info));
> >> claimed_files[num_claimed_files - 1] = lto_file;
> >> + pthread_mutex_unlock (&plugin_lock);
> >>
> >> *claimed = 1;
> >> }
> >>
> >> + pthread_mutex_lock (&plugin_lock);
> >> if (offload_files == NULL)
> >> {
> >> /* Add dummy item to the start of the list. */
> >> @@ -1333,11 +1340,12 @@ claim_file_handler (const struct
> >> ld_plugin_input_file *file, int *claimed)
> >> offload_files_last_lto = ofld;
> >> num_offload_files++;
> >> }
> >> + pthread_mutex_unlock (&plugin_lock);
> >>
> >> goto cleanup;
> >>
> >> err:
> >> - non_claimed_files++;
> >> + __atomic_fetch_add (&non_claimed_files, 1, __ATOMIC_RELAXED);
> >
> > is it worth "optimizing" this with yet another need for target specific
> > support
> > (just use pthread_mutex here as well?)
>
> Sure.
>
> May I install the patch with the change?
Can you at least add a configure check for pthread.h and maybe disable
locking when not found or erroring out? I figure we have GCC_AC_THREAD_HEADER
for the gthr.h stuff using $target_thread_file (aka --enable-threads=XYZ),
but as said that's for the target and I don't see any host uses. We might also
add an explicit list of hosts (*-linux*?) where we enable thread support for
lto-plugin, providing opt-in (so you'd have to wrap the mutex taking or
if-def it out).
I think you also need to link lto-plugin with -pthread, no? On linux
it might work omitting that but I'm not sure other libc have serial pthread
stubs in their libc. BFD ld definitely doesn't link against pthread so
dlopening lto-plugin will fail (also not all libc might like
initializing threads
from a dlopen _init).
Richard.
> Cheers,
> Martin
>
> >
> >> free (lto_file.name);
> >>
> >> cleanup:
> >> @@ -1415,6 +1423,12 @@ onload (struct ld_plugin_tv *tv)
> >> struct ld_plugin_tv *p;
> >> enum ld_plugin_status status;
> >>
> >> + if (pthread_mutex_init (&plugin_lock, NULL) != 0)
> >> + {
> >> + fprintf (stderr, "mutex init failed\n");
> >> + abort ();
> >> + }
> >> +
> >> p = tv;
> >> while (p->tv_tag)
> >> {
> >> --
> >> 2.36.1
> >>
> >>
