From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 5535 invoked by alias); 11 Dec 2013 19:58:30 -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 5525 invoked by uid 89); 11 Dec 2013 19:58:29 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-4.2 required=5.0 tests=AWL,BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 11 Dec 2013 19:58:28 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id rBBJwOrA009634 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 11 Dec 2013 14:58:25 -0500 Received: from host2.jankratochvil.net (ovpn-116-40.ams2.redhat.com [10.36.116.40]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id rBBJwKTq026006 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Wed, 11 Dec 2013 14:58:23 -0500 Date: Wed, 11 Dec 2013 19:58:00 -0000 From: Jan Kratochvil To: Markus Metzger Cc: gdb-patches@sourceware.org, Pedro Alves Subject: Re: [patch v7 22/24] btrace, gdbserver: read branch trace incrementally Message-ID: <20131211195820.GB22687@host2.jankratochvil.net> References: <1385735899-12481-1-git-send-email-markus.t.metzger@intel.com> <1385735899-12481-23-git-send-email-markus.t.metzger@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1385735899-12481-23-git-send-email-markus.t.metzger@intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-IsSubscribed: yes X-SW-Source: 2013-12/txt/msg00450.txt.bz2 On Fri, 29 Nov 2013 15:38:17 +0100, Markus Metzger wrote: > @@ -717,27 +717,152 @@ btrace_teardown (struct thread_info *tp) > btrace_clear (tp); > } > > +/* Adjust the block trace in order to stitch old and new trace together. > + BTRACE is the new delta trace between the last and the current stop. > + BTINFO is the old branch trace until the last stop. > + May modifx BTRACE as well as the existing trace in BTINFO. modify > + Return 0 on success, -1 otherwise. */ > + > +static int > +btrace_stitch_trace (VEC (btrace_block_s) **btrace, > + const struct btrace_thread_info *btinfo) > +{ > + struct btrace_function *end; > + struct btrace_insn *insn; > + btrace_block_s *block; > + > + /* If we don't have trace, there's nothing to do. */ > + if (VEC_empty (btrace_block_s, *btrace)) > + return 0; > + > + end = btinfo->end; > + gdb_assert (end != NULL); > + > + block = VEC_last (btrace_block_s, *btrace); > + insn = VEC_last (btrace_insn_s, end->insn); At least call block and insn somehow specific from where they come from. Maybe btrace_block and btinfo_end. Also end should be called btinfo_end (if the extra variable still makes sense in such case). I would even call it new_btrace and old_btinfo with variables old_end etc. > + > + /* If the current PC at the end of the block is the same as in our current > + trace, there are two explanations: > + 1. we executed the instruction and some branch brought us back. > + 2. we have not made any progress. > + In the first case, the delta trace vector should contain at least two > + entries. > + In the second case, the delta trace vector should contain exactly one > + entry for the partial block containing the current PC. Remove it. */ > + if (block->end == insn->pc && VEC_length (btrace_block_s, *btrace) == 1) > + { > + VEC_pop (btrace_block_s, *btrace); > + return 0; > + } > + > + DEBUG ("stitching %s to %s", ftrace_print_insn_addr (insn), > + core_addr_to_string_nz (block->end)); > + > + /* Do a simple sanity check to make sure we don't accidentally end up > + with a bad block. This should not occur in practice. */ > + if (block->end < insn->pc) > + { > + warning (_("Error while trying to read delta trace. Falling back to " > + "a full read.")); > + return -1; > + } > + > + /* We adjust the last block to start at the end of our current trace. */ > + gdb_assert (block->begin == 0); > + block->begin = insn->pc; > + > + /* We simply pop the last insn so we can insert it again as part of > + the normal branch trace computation. > + Since instruction iterators are based on indices in the instructions > + vector, we don't leave any pointers dangling. */ > + DEBUG ("pruning insn at %s for stitching", ftrace_print_insn_addr (insn)); > + > + VEC_pop (btrace_insn_s, end->insn); > + > + /* The instructions vector may become empty temporarily if this has > + been the only instruction in this function segment. > + This violates the invariant but will be remedied shortly. */ > + return 0; > +} [...] Thanks, Jan