https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97461
--- Comment #20 from Sergei Trofimovich <slyfox at gcc dot gnu.org> --- (In reply to Martin Liška from comment #17) > Or I may have a smarter trick: let's do dry run of malloc/free functions > early in __gcov_init. Can you please test the patch as well? > > commit d80cecdb87d159f0b3a4072b6e1ef80515ad2afb > Author: Martin Liska <mli...@suse.cz> > Date: Thu Oct 29 19:52:37 2020 +0100 > > PGO: use dry run of malloc and free functions. > > diff --git a/libgcc/libgcov-driver.c b/libgcc/libgcov-driver.c > index e53e4dc392a..dd481b48e22 100644 > --- a/libgcc/libgcov-driver.c > +++ b/libgcc/libgcov-driver.c > @@ -608,12 +608,25 @@ __gcov_exit (void) > gcov_error_exit (); > } > > +/* Test memory that forces malloc and free functions to be called early > + so that allocate_gcov_kvp can use calloc. Indirect call counters > + taken from a pre-allocated array are used before that. */ > +char *__gcov_test_memory; > + > /* Add a new object file onto the bb chain. Invoked automatically > when running an object file's global ctors. */ > > void > __gcov_init (struct gcov_info *info) > { > + static int malloc_utilized = 0; > + if (!malloc_utilized) > + { > + __gcov_test_memory = malloc (16); > + free (__gcov_test_memory); > + malloc_utilized = 1; > + } > + > if (!info->version || !info->n_functions) > return; > if (gcov_version (info, info->version, 0)) Did not seem to help (I only applied the patch, did not bump GCOV_PREALLOCATED_KVP 64 to 128). The backtrace of new deadlock: (gdb) bt #0 __lll_lock_wait (futex=0x7eff76800018, private=0) at lowlevellock.c:52 #1 0x00007eff76f5f305 in __GI___pthread_mutex_lock (mutex=0x7eff76800018) at ../nptl/pthread_mutex_lock.c:135 #2 0x0000563beb0fd171 in arena_t::MallocSmall(unsigned long, bool) () #3 0x0000563beb0fe09c in arena_t::Malloc(unsigned long, bool) () #4 0x0000563beb0ff212 in calloc () #5 0x0000563beb1efa5b in allocate_gcov_kvp () at /var/tmp/portage/sys-devel/gcc-11.0.0_pre9999/work/gcc-11.0.0_pre9999/libgcc/libgcov.h:431 #6 gcov_topn_add_value (count=1, use_atomic=1, increment_total=1, value=496, counters=0x563beb2608c0 <__gcov3._ZL20arena_run_reg_dallocP11arena_run_tP11arena_bin_tPvm>) at /var/tmp/portage/sys-devel/gcc-11.0.0_pre9999/work/gcc-11.0.0_pre9999/libgcc/libgcov.h:477 #7 __gcov_topn_values_profiler_body (use_atomic=1, value=496, counters=0x563beb2608c0 <__gcov3._ZL20arena_run_reg_dallocP11arena_run_tP11arena_bin_tPvm>) at /var/tmp/portage/sys-devel/gcc-11.0.0_pre9999/work/gcc-11.0.0_pre9999/libgcc/libgcov-profiler.c:103 #8 __gcov_topn_values_profiler_atomic (counters=0x563beb2608c0 <__gcov3._ZL20arena_run_reg_dallocP11arena_run_tP11arena_bin_tPvm>, value=496) at /var/tmp/portage/sys-devel/gcc-11.0.0_pre9999/work/gcc-11.0.0_pre9999/libgcc/libgcov-profiler.c:128 #9 0x0000563beb0fc085 in arena_t::DallocSmall(arena_chunk_t*, void*, arena_chunk_map_t*) () #10 0x0000563beb0fc68c in free () #11 0x00007eff59e73047 in driConcatConfigs () at /usr/lib64/dri/swrast_dri.so #12 0x00007eff599f6714 in dri_init_screen_helper () at /usr/lib64/dri/swrast_dri.so #13 0x00007eff599efe63 in drisw_init_screen () at /usr/lib64/dri/swrast_dri.so #14 0x00007eff59e73c15 in driCreateNewScreen2 () at /usr/lib64/dri/swrast_dri.so #15 0x00007eff5a536c44 in driswCreateScreen () at /usr/lib64/libGLX_mesa.so.0 #16 0x00007eff5a53ce10 in __glXInitialize () at /usr/lib64/libGLX_mesa.so.0 #17 0x00007eff5a539371 in glXQueryServerString () at /usr/lib64/libGLX_mesa.so.0 #18 0x00007eff74f82b79 in epoxy_glx_version () at /usr/lib64/libepoxy.so.0 #19 0x00007eff75373645 in gdk_x11_screen_init_gl () at /usr/lib64/libgdk-3.so.0 #20 0x00007eff753739ea in _gdk_x11_screen_update_visuals_for_gl () at /usr/lib64/libgdk-3.so.0 #21 0x00007eff7537c9d8 in _gdk_x11_screen_init_visuals () at /usr/lib64/libgdk-3.so.0 #22 0x00007eff753799ab in _gdk_x11_screen_new () at /usr/lib64/libgdk-3.so.0 #23 0x00007eff75369450 in _gdk_x11_display_open () at /usr/lib64/libgdk-3.so.0 #24 0x00007eff7533b8c8 in gdk_display_manager_open_display () at /usr/lib64/libgdk-3.so.0 #25 0x00007eff697ad710 in XREMain::XRE_mainStartup(bool*) () at /home/slyfox/tmp/portage/www-client/firefox-82.0/work/firefox_build/instrumented/dist/firefox/libxul.so #26 0x00007eff697b2bd5 in XREMain::XRE_main(int, char**, mozilla::BootstrapConfig const&) () at /home/slyfox/tmp/portage/www-client/firefox-82.0/work/firefox_build/instrumented/dist/firefox/libxul.so #27 0x00007eff697b3bf3 in XRE_main(int, char**, mozilla::BootstrapConfig const&) () at /home/slyfox/tmp/portage/www-client/firefox-82.0/work/firefox_build/instrumented/dist/firefox/libxul.so #28 0x00007eff697bc280 in mozilla::BootstrapImpl::XRE_main(int, char**, mozilla::BootstrapConfig const&) () at /home/slyfox/tmp/portage/www-client/firefox-82.0/work/firefox_build/instrumented/dist/firefox/libxul.so #29 0x0000563beb0e53a0 in do_main(int, char**, char**) () #30 0x0000563beb0e30d1 in main () I suspect that this custom malloc hits TOPN (and resizes dynamic array) frequently.