From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-23.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0290C43381 for ; Tue, 23 Feb 2021 14:58:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A1A3B64E20 for ; Tue, 23 Feb 2021 14:58:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232258AbhBWO6N (ORCPT ); Tue, 23 Feb 2021 09:58:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35162 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232066AbhBWO6C (ORCPT ); Tue, 23 Feb 2021 09:58:02 -0500 Received: from mail-qk1-x730.google.com (mail-qk1-x730.google.com [IPv6:2607:f8b0:4864:20::730]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6624C06178C for ; Tue, 23 Feb 2021 06:57:18 -0800 (PST) Received: by mail-qk1-x730.google.com with SMTP id 204so11403705qke.11 for ; Tue, 23 Feb 2021 06:57:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=LmrazInE9lkHVfTVT/c9ri5uOiLTKO8Po9aKcmrNBAY=; b=lPGcs8+XN3ZhWjVfUavOT+6rAWT08aaeXOP+i0kowIIBYo9WhUzverN7jPlsTiao8N Dsh0tpbLvYdVtf3jpRizZ1sub2i15T6IvYNm6KOy79b2VfnDv01x/1WP/06N5TEXCPvK ks31czjm8XJoxoKwMTPR61Wpm52jhrg/b5h0lhp1zsIFoxgM/XTerBw6sRWLdQL+/q4B R3IBD3hWUe+/7M45KI932Aoi2d/fOuhsL9ZuoTPMMGhuIzFgitBPsh4dDGzQtpn4jvCg 3v7HHGk73/z4DgE6CrT1ht0NL9IWXRrD9YLxTDwKy9t7WXvPvb81TuXjDk2KSlm0SyIL jAKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=LmrazInE9lkHVfTVT/c9ri5uOiLTKO8Po9aKcmrNBAY=; b=YY11HGnhybQluQMaH/3EISnRWhelvbGrCinbeZ+4w9uooo2KkPuFnAsAaLITNz/LC5 mjnsn2oxhvCNUXsl/9sQQ5J5hAz6t8lNc43iyfXDOnvC6J90i6I2a9xeeefMou/yw0tN TtDGXFxEHo5XaXXhR5ZnZewO9gQurm5HreBVo2J93VGIzyOet2m13KQhhAFTatE5bUZJ TS4Le69HWKHZ7Bj9nCmuoDd3tTg2zYLji/4cjsYpPxRcqLxEaDFEOCLlBBa/TbJLfKYC i+XVp0KVtdJhSoWoxIALETBZGMaJXuxNgryi3HLssMAXAVh45+JSqZtH/JxKrkO3foAa KFLw== X-Gm-Message-State: AOAM530CZXiz6dLCpCYbVdkd9J9c02sIX3fFE0L5+FyjOD+EO3Mcnk2i JufenbHF5Zxfxj3PaY9cb0PGgl2KbYSWelVS6fwlLQ== X-Google-Smtp-Source: ABdhPJxskRNcDrPojVCsfatXoteGeJRu+C8kFTCNr9W1n27qH/CtTomH+2quLi9leH/3XygPSui+HOsTQSf1jHotd2I= X-Received: by 2002:a37:a757:: with SMTP id q84mr25540114qke.501.1614092237384; Tue, 23 Feb 2021 06:57:17 -0800 (PST) MIME-Version: 1.0 References: <20210223143426.2412737-1-elver@google.com> <20210223143426.2412737-4-elver@google.com> In-Reply-To: <20210223143426.2412737-4-elver@google.com> From: Dmitry Vyukov Date: Tue, 23 Feb 2021 15:57:06 +0100 Message-ID: Subject: Re: [PATCH RFC 3/4] perf/core: Add support for SIGTRAP on perf events To: Marco Elver Cc: Peter Zijlstra , Alexander Shishkin , Arnaldo Carvalho de Melo , Ingo Molnar , Jiri Olsa , Mark Rutland , Namhyung Kim , Thomas Gleixner , Alexander Potapenko , Al Viro , Arnd Bergmann , Christian Brauner , Jann Horn , Jens Axboe , Matt Morehouse , Peter Collingbourne , Ian Rogers , kasan-dev , linux-arch , linux-fsdevel , LKML , linux-m68k@lists.linux-m68k.org, "the arch/x86 maintainers" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Feb 23, 2021 at 3:34 PM Marco Elver wrote: > > Adds bit perf_event_attr::sigtrap, which can be set to cause events to > send SIGTRAP (with si_code TRAP_PERF) to the task where the event > occurred. To distinguish perf events and allow user space to decode > si_perf (if set), the event type is set in si_errno. > > The primary motivation is to support synchronous signals on perf events > in the task where an event (such as breakpoints) triggered. > > Link: https://lore.kernel.org/lkml/YBv3rAT566k+6zjg@hirez.programming.kicks-ass.net/ > Suggested-by: Peter Zijlstra > Signed-off-by: Marco Elver > --- > include/uapi/linux/perf_event.h | 3 ++- > kernel/events/core.c | 21 +++++++++++++++++++++ > 2 files changed, 23 insertions(+), 1 deletion(-) > > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > index ad15e40d7f5d..b9cc6829a40c 100644 > --- a/include/uapi/linux/perf_event.h > +++ b/include/uapi/linux/perf_event.h > @@ -389,7 +389,8 @@ struct perf_event_attr { > cgroup : 1, /* include cgroup events */ > text_poke : 1, /* include text poke events */ > build_id : 1, /* use build id in mmap2 events */ > - __reserved_1 : 29; > + sigtrap : 1, /* send synchronous SIGTRAP on event */ > + __reserved_1 : 28; > > union { > __u32 wakeup_events; /* wakeup every n events */ > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 37a8297be164..8718763045fd 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -6288,6 +6288,17 @@ void perf_event_wakeup(struct perf_event *event) > } > } > > +static void perf_sigtrap(struct perf_event *event) > +{ > + struct kernel_siginfo info; > + > + clear_siginfo(&info); > + info.si_signo = SIGTRAP; > + info.si_code = TRAP_PERF; > + info.si_errno = event->attr.type; > + force_sig_info(&info); > +} > + > static void perf_pending_event_disable(struct perf_event *event) > { > int cpu = READ_ONCE(event->pending_disable); > @@ -6297,6 +6308,13 @@ static void perf_pending_event_disable(struct perf_event *event) > > if (cpu == smp_processor_id()) { > WRITE_ONCE(event->pending_disable, -1); > + > + if (event->attr.sigtrap) { > + atomic_inc(&event->event_limit); /* rearm event */ Can/should this be atomic_set(&event->event_limit, 1)? It should only go between 1 and 0, right? Otherwise: Acked-by: Dmitry Vyukov > + perf_sigtrap(event); > + return; > + } > + > perf_event_disable_local(event); > return; > } > @@ -11325,6 +11343,9 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, > > event->state = PERF_EVENT_STATE_INACTIVE; > > + if (event->attr.sigtrap) > + atomic_set(&event->event_limit, 1); > + > if (task) { > event->attach_state = PERF_ATTACH_TASK; > /* > -- > 2.30.0.617.g56c4b15f3c-goog >