From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 65343 invoked by alias); 29 Nov 2018 14:05:01 -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 65281 invoked by uid 89); 29 Nov 2018 14:05:00 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-26.9 required=5.0 tests=BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,RCVD_IN_DNSWL_NONE,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 spammy=Clearly, boxes, Apple, 20181120 X-HELO: EUR01-HE1-obe.outbound.protection.outlook.com Received: from mail-eopbgr130058.outbound.protection.outlook.com (HELO EUR01-HE1-obe.outbound.protection.outlook.com) (40.107.13.58) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 29 Nov 2018 14:04:57 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=armh.onmicrosoft.com; s=selector1-arm-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=0rCAf86OHHuP8pYWTiBs8FeShjCH0fIb1h/gmKt+mPU=; b=OI7JncPcL6okEnM6+qWtTGIT96KeRr5cQjhqr7jpTT5nqZockITUQbOBsr0cV4AgJAWdTfipbBpo3LqPmtJBwl/NNZUCz8yhkXjKtjOUeu74ROPAtsUrazP9CIpDLxAuq3+4KXrlaFjdlNQlGMf1h919Vq8oeclGLJlScHQLvXI= Received: from DB6PR0802MB2133.eurprd08.prod.outlook.com (10.172.226.148) by DB6PR0802MB2263.eurprd08.prod.outlook.com (10.172.227.148) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.1382.18; Thu, 29 Nov 2018 14:04:53 +0000 Received: from DB6PR0802MB2133.eurprd08.prod.outlook.com ([fe80::fd61:f010:9962:229]) by DB6PR0802MB2133.eurprd08.prod.outlook.com ([fe80::fd61:f010:9962:229%8]) with mapi id 15.20.1382.017; Thu, 29 Nov 2018 14:04:53 +0000 From: Alan Hayward To: "gdb-patches@sourceware.org" CC: nd Subject: [Ping][PATCH] AArch64: Racy: Don't set empty set of hardware BPs/WPs on new thread Date: Thu, 29 Nov 2018 14:05:00 -0000 Message-ID: <6911C9CA-CE47-421F-8E2D-2149C08B68AD@arm.com> References: <20181120115602.30606-1-alan.hayward@arm.com> In-Reply-To: <20181120115602.30606-1-alan.hayward@arm.com> authentication-results: spf=none (sender IP is ) smtp.mailfrom=Alan.Hayward@arm.com; received-spf: None (protection.outlook.com: arm.com does not designate permitted sender hosts) Content-Type: text/plain; charset="us-ascii" Content-ID: <9FF1226E9B52464A97637D4987F78D7B@eurprd08.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-IsSubscribed: yes X-SW-Source: 2018-11/txt/msg00532.txt.bz2 Ping! > On 20 Nov 2018, at 11:56, Alan Hayward wrote: >=20 > [Note: I hope to eventually isolate the exact kernel/hardware issue and > raise a bug elsewhere against that.] >=20 > On some heavily loaded AArch64 boxes, GDB will sometimes hang forever when > the inferior creates a thread. This hang happens inside the kernel during > the ptrace call to set hardware watchpoints or hardware breakpoints. > Currently, GDB will always set hw wp/bp at the start of each thread even = if > there are none set in the process. >=20 > This patch works around the issue by avoiding setting hw wp/bp if there > are none set for the process. >=20 > On an effected machine, this fix drastically reduces the racy nature of t= he > gdb.threads test set. I ran the entire gdb test suite across all process= ors > for 100 iterations, then ran the results through the racy tests script. > Without the patch, 58 .exp files in gdb.threads were marked as racy. Aft= er > the patch this reduced to the same ~14 tests as the non effected boxes. >=20 > Clearly GDB will still be subject to hangs on an effect box if hw wp/bp's= are > used prior to creating inferior threads on a heavily loaded system. >=20 > To enable this in gdbserver, the sequence in gdbserver add_lwp() is switc= hed > to the same as gdb order as gdb, to ensure the thread is registered before > calling new_thread(). This allows aarch64_linux_new_thread() to read the > ptid. >=20 > gdb/ChangeLog: >=20 > 2018-11-20 Alan Hayward >=20 > * nat/aarch64-linux-hw-point.c > (aarch64_linux_any_set_debug_regs_state): New function. > * nat/aarch64-linux-hw-point.h > (aarch64_linux_any_set_debug_regs_state): New declaration. > * nat/aarch64-linux.c (aarch64_linux_new_thread): Check if any > BPs or WPs are set. >=20 > gdb/gdbserver/ChangeLog: >=20 > 2018-11-20 Alan Hayward >=20 > * linux-low.c (add_lwp): Switch ordering. > --- > gdb/gdbserver/linux-low.c | 4 ++-- > gdb/nat/aarch64-linux-hw-point.c | 23 +++++++++++++++++++++++ > gdb/nat/aarch64-linux-hw-point.h | 6 ++++++ > gdb/nat/aarch64-linux.c | 15 ++++++++++----- > 4 files changed, 41 insertions(+), 7 deletions(-) >=20 > diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c > index 701f3e863c..1c336efade 100644 > --- a/gdb/gdbserver/linux-low.c > +++ b/gdb/gdbserver/linux-low.c > @@ -951,11 +951,11 @@ add_lwp (ptid_t ptid) >=20 > lwp->waitstatus.kind =3D TARGET_WAITKIND_IGNORE; >=20 > + lwp->thread =3D add_thread (ptid, lwp); > + > if (the_low_target.new_thread !=3D NULL) > the_low_target.new_thread (lwp); >=20 > - lwp->thread =3D add_thread (ptid, lwp); > - > return lwp; > } >=20 > diff --git a/gdb/nat/aarch64-linux-hw-point.c b/gdb/nat/aarch64-linux-hw-= point.c > index 18b5af2d49..7f96fa2b7a 100644 > --- a/gdb/nat/aarch64-linux-hw-point.c > +++ b/gdb/nat/aarch64-linux-hw-point.c > @@ -717,6 +717,29 @@ aarch64_linux_set_debug_regs (struct aarch64_debug_r= eg_state *state, > } > } >=20 > +/* See nat/aarch64-linux-hw-point.h. */ > + > +bool > +aarch64_linux_any_set_debug_regs_state (struct aarch64_debug_reg_state *= state, > + bool watchpoint) > +{ > + int i, count; > + const CORE_ADDR *addr; > + const unsigned int *ctrl; > + > + count =3D watchpoint ? aarch64_num_wp_regs : aarch64_num_bp_regs; > + addr =3D watchpoint ? state->dr_addr_wp : state->dr_addr_bp; > + ctrl =3D watchpoint ? state->dr_ctrl_wp : state->dr_ctrl_bp; > + if (count =3D=3D 0) > + return false; > + > + for (i =3D 0; i < count; i++) > + if (addr[i] !=3D 0 || ctrl[i] !=3D 0) > + return true; > + > + return false; > +} > + > /* Print the values of the cached breakpoint/watchpoint registers. */ >=20 > void > diff --git a/gdb/nat/aarch64-linux-hw-point.h b/gdb/nat/aarch64-linux-hw-= point.h > index 1940b06a89..37107a888c 100644 > --- a/gdb/nat/aarch64-linux-hw-point.h > +++ b/gdb/nat/aarch64-linux-hw-point.h > @@ -182,6 +182,12 @@ int aarch64_handle_watchpoint (enum target_hw_bp_typ= e type, CORE_ADDR addr, > void aarch64_linux_set_debug_regs (struct aarch64_debug_reg_state *state, > int tid, int watchpoint); >=20 > +/* Return TRUE if there are any hardware breakpoints. If WATCHPOINT is = TRUE, > + check hardware watchpoints instead. */ > +bool > +aarch64_linux_any_set_debug_regs_state (struct aarch64_debug_reg_state *= state, > + bool watchpoint); > + > void aarch64_show_debug_reg_state (struct aarch64_debug_reg_state *state, > const char *func, CORE_ADDR addr, > int len, enum target_hw_bp_type type); > diff --git a/gdb/nat/aarch64-linux.c b/gdb/nat/aarch64-linux.c > index 0f2c8011ea..48c59f6288 100644 > --- a/gdb/nat/aarch64-linux.c > +++ b/gdb/nat/aarch64-linux.c > @@ -73,13 +73,18 @@ aarch64_linux_prepare_to_resume (struct lwp_info *lwp) > void > aarch64_linux_new_thread (struct lwp_info *lwp) > { > + ptid_t ptid =3D ptid_of_lwp (lwp); > + struct aarch64_debug_reg_state *state > + =3D aarch64_get_debug_reg_state (ptid.pid ()); > struct arch_lwp_info *info =3D XNEW (struct arch_lwp_info); >=20 > - /* Mark that all the hardware breakpoint/watchpoint register pairs > - for this thread need to be initialized (with data from > - aarch_process_info.debug_reg_state). */ > - DR_MARK_ALL_CHANGED (info->dr_changed_bp, aarch64_num_bp_regs); > - DR_MARK_ALL_CHANGED (info->dr_changed_wp, aarch64_num_wp_regs); > + /* If there are hardware breakpoints/watchpoints in the process then m= ark that > + all the hardware breakpoint/watchpoint register pairs for this thre= ad need > + to be initialized (with data from aarch_process_info.debug_reg_stat= e). */ > + if (aarch64_linux_any_set_debug_regs_state (state, false)) > + DR_MARK_ALL_CHANGED (info->dr_changed_bp, aarch64_num_bp_regs); > + if (aarch64_linux_any_set_debug_regs_state (state, true)) > + DR_MARK_ALL_CHANGED (info->dr_changed_wp, aarch64_num_wp_regs); >=20 > lwp_set_arch_private_info (lwp, info); > } > --=20 > 2.17.2 (Apple Git-113) >=20