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Biederman) To: Oleg Nesterov Cc: Jens Axboe , Linus Torvalds , io-uring , Linux Kernel Mailing List , Stefan Metzmacher References: <20210325164343.807498-1-axboe@kernel.dk> <3a1c02a5-db6d-e3e1-6ff5-69dd7cd61258@kernel.dk> <20210325204014.GD28349@redhat.com> Date: Thu, 25 Mar 2021 15:48:59 -0500 In-Reply-To: <20210325204014.GD28349@redhat.com> (Oleg Nesterov's message of "Thu, 25 Mar 2021 21:40:15 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1lPWvX-007lPx-DU;;;mid=;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1+s4dSqXk5VKFAiX0d5kYypYa8oLuycJ/k= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on sa04.xmission.com X-Spam-Level: ** X-Spam-Status: No, score=2.0 required=8.0 tests=ALL_TRUSTED,BAYES_50, DCC_CHECK_NEGATIVE,T_TM2_M_HEADER_IN_MSG,T_TooManySym_01, T_TooManySym_02,T_TooManySym_03,T_TooManySym_04,XMNoVowels,XMSubLong autolearn=disabled version=3.4.2 X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.5000] * 0.7 XMSubLong Long Subject * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa04 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_02 5+ unique symbols in subject * 0.0 T_TooManySym_03 6+ unique symbols in subject * 0.0 T_TooManySym_04 7+ unique symbols in subject * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa04 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: **;Oleg Nesterov X-Spam-Relay-Country: X-Spam-Timing: total 238 ms - load_scoreonly_sql: 0.18 (0.1%), signal_user_changed: 12 (4.9%), b_tie_ro: 10 (4.1%), parse: 1.10 (0.5%), extract_message_metadata: 3.4 (1.4%), get_uri_detail_list: 0.95 (0.4%), tests_pri_-1000: 4.1 (1.7%), tests_pri_-950: 1.34 (0.6%), tests_pri_-900: 0.97 (0.4%), tests_pri_-90: 49 (20.5%), check_bayes: 47 (20.0%), b_tokenize: 4.8 (2.0%), b_tok_get_all: 6 (2.5%), b_comp_prob: 1.83 (0.8%), b_tok_touch_all: 32 (13.6%), b_finish: 0.71 (0.3%), tests_pri_0: 143 (60.2%), check_dkim_signature: 0.57 (0.2%), check_dkim_adsp: 2.7 (1.1%), poll_dns_idle: 1.23 (0.5%), tests_pri_10: 1.84 (0.8%), tests_pri_500: 13 (5.5%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCH 0/2] Don't show PF_IO_WORKER in /proc//task/ X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg Nesterov writes: > On 03/25, Eric W. Biederman wrote: >> >> So looking quickly the flip side of the coin is gdb (and other >> debuggers) needs a way to know these threads are special, so it can know >> not to attach. > > may be, > >> I suspect getting -EPERM (or possibly a different error code) when >> attempting attach is the right was to know that a thread is not >> available to be debugged. > > may be. > > But I don't think we can blame gdb. The kernel changed the rules, and this > broke gdb. IOW, I don't agree this is gdb bug. My point would be it is not strictly a regression either. It is gdb not handling new functionality. If we can be backwards compatible and make ptrace_attach work that is preferable. If we can't saying the handful of ptrace using applications need an upgrade to support processes that use io_uring may be acceptable. I don't see any easy to implement path that is guaranteed to work. Eric