From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 73052 invoked by alias); 15 Oct 2019 23:20:28 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 73043 invoked by uid 89); 15 Oct 2019 23:20:28 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-18.3 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3 autolearn=ham version=3.3.1 spammy=uploaded, HContent-Transfer-Encoding:8bit X-HELO: mx1.osci.io Received: from polly.osci.io (HELO mx1.osci.io) (8.43.85.229) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 15 Oct 2019 23:20:27 +0000 Received: by mx1.osci.io (Postfix, from userid 994) id 7349D20674; Tue, 15 Oct 2019 19:20:25 -0400 (EDT) Received: from gnutoolchain-gerrit.osci.io (gnutoolchain-gerrit.osci.io [8.43.85.239]) by mx1.osci.io (Postfix) with ESMTP id 60B49205E7; Tue, 15 Oct 2019 19:20:24 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by gnutoolchain-gerrit.osci.io (Postfix) with ESMTP id 3BFFE26976; Tue, 15 Oct 2019 19:20:24 -0400 (EDT) X-Gerrit-PatchSet: 1 Date: Tue, 15 Oct 2019 23:20:00 -0000 From: "Christian Biesinger (Code Review)" To: gdb-patches@sourceware.org Cc: Christian Biesinger Message-ID: Auto-Submitted: auto-generated X-Gerrit-MessageType: newchange Subject: [review] Don't save the signal state in SIGSETJMP X-Gerrit-Change-Id: Ib3010966050c64b4cc8b47d8cb45871652b0b3ea X-Gerrit-Change-Number: 124 X-Gerrit-ChangeURL: X-Gerrit-Commit: 8fcd192ea7755afd1ae6423acc957e5b77fae861 References: Reply-To: cbiesinger@google.com, cbiesinger@google.com, gdb-patches@sourceware.org MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Disposition: inline User-Agent: Gerrit/3.0.3 Content-Type: text/plain; charset=UTF-8 X-SW-Source: 2019-10/txt/msg00463.txt.bz2 Christian Biesinger has uploaded a new change for review. Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/124 ...................................................................... Don't save the signal state in SIGSETJMP Saving the signal state is very slow (this patch is a 14% speedup). The reason we need this code is because signal handler will leave the signal blocked when we longjmp out of it. But in this case we can just manually unblock the signal instead of taking the unconditional perf hit. gdb/ChangeLog: 2019-10-15 Christian Biesinger * gdbsupport/gdb_setjmp.h (SIGSETJMP): Allow passing in the value to pass on to sigsetjmp's second argument. * cp-support.c (gdb_demangle): Unblock SIGSEGV if we caught a crash. Change-Id: Ib3010966050c64b4cc8b47d8cb45871652b0b3ea --- M gdb/cp-support.c M gdb/gdbsupport/gdb_setjmp.h 2 files changed, 22 insertions(+), 3 deletions(-) diff --git a/gdb/cp-support.c b/gdb/cp-support.c index cd732b6..253369b 100644 --- a/gdb/cp-support.c +++ b/gdb/cp-support.c @@ -1539,7 +1539,16 @@ ofunc = signal (SIGSEGV, gdb_demangle_signal_handler); #endif - crash_signal = SIGSETJMP (gdb_demangle_jmp_buf); + /* The signal handler may keep the signal blocked when we longjmp out + of it. If we have sigprocmask, we can use it to unblock the signal + afterwards and we can avoid the performance overhead of saving the + signal mask just in case the signal gets triggered. Otherwise, just + tell sigsetjmp to save the mask. */ +#ifdef HAVE_SIGPROCMASK + crash_signal = SIGSETJMP (gdb_demangle_jmp_buf, 0); +#else + crash_signal = SIGSETJMP (gdb_demangle_jmp_buf, 1); +#endif } #endif @@ -1559,6 +1568,14 @@ { static int error_reported = 0; +#ifdef HAVE_SIGPROCMASK + /* If we got the signal, SIGSEGV may still be blocked; restore it. */ + sigset_t segv_sig_set; + sigemptyset (&segv_sig_set); + sigaddset (&segv_sig_set, SIGSEGV); + sigprocmask (SIG_UNBLOCK, &segv_sig_set, NULL); +#endif + if (!error_reported) { std::string short_msg diff --git a/gdb/gdbsupport/gdb_setjmp.h b/gdb/gdbsupport/gdb_setjmp.h index d4ebbfa..4995970 100644 --- a/gdb/gdbsupport/gdb_setjmp.h +++ b/gdb/gdbsupport/gdb_setjmp.h @@ -23,11 +23,13 @@ #ifdef HAVE_SIGSETJMP #define SIGJMP_BUF sigjmp_buf -#define SIGSETJMP(buf) sigsetjmp((buf), 1) +#define SIGSETJMP(buf,val) sigsetjmp((buf), val) #define SIGLONGJMP(buf,val) siglongjmp((buf), (val)) #else #define SIGJMP_BUF jmp_buf -#define SIGSETJMP(buf) setjmp(buf) +/* We ignore val here because that's safer and avoids having to check + whether _setjmp exists. */ +#define SIGSETJMP(buf,val) setjmp(buf) #define SIGLONGJMP(buf,val) longjmp((buf), (val)) #endif