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charset="us-ascii"; Format="flowed" Errors-To: lttng-dev-bounces@lists.lttng.org Sender: "lttng-dev" On 2022-09-22 05:15, Eric Wong via lttng-dev wrote: > Hello, I'm using urcu-bp + rculfhash + call_rcu to implement > malloc instrumentation (via LD_PRELOAD) on an existing > single-threaded Perl codebase which uses Linux signalfd. > > signalfd depends on signals being blocked in all threads > of the process, otherwise threads with unblocked signals > can receive them and starve the signalfd. > > While some threads in URCU do block signals (e.g. workqueue > worker for rculfhash), the call_rcu thread and rculfhash > partition_resize_helper threads do not... > > Should all threads URCU creates block signals (aside from SIGRCU)? Yes, I think you are right. The SIGRCU signal is only needed for the urcu-signal flavor though. Would you like to submit a patch ? Thanks, Mathieu > > There might be other places, too, I haven't looked too closely... > > Anyways, I'm currently relying on this workaround to ensure > initial calls to call_rcu and cds_lfht_resize are run with > signals blocked: > > /* error-checking omitted for brevity */ > __attribute__((constructor)) static void my_ctor(void) > { > sigset_t set, old; > struct foo_hdr *h; > > sigfillset(&set); > pthread_sigmask(SIG_SETMASK, &set, &old); > > g_tbl = cds_lfht_new(8192, 1, 0, CDS_LFHT_AUTO_RESIZE, 0); > > h = malloc(sizeof(struct foo_hdr))); > if (h) /* force call_rcu to start background thread */ > call_rcu(&h->as.dead, free_foo_hdr_rcu); > > /* start more background threads before unblocking signals */ > cds_lfht_resize(g_tbl, 16384); > > pthread_sigmask(SIG_SETMASK, &old, NULL); > } > > But I suspect it's better to ensure signals are blocked in all > URCU-created threads... > > Thanks. > _______________________________________________ > lttng-dev mailing list > lttng-dev@lists.lttng.org > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev