From mboxrd@z Thu Jan 1 00:00:00 1970 From: Enke Chen Subject: Re: [PATCH v3] kernel/signal: Signal-based pre-coredump notification Date: Wed, 24 Oct 2018 15:02:29 -0700 Message-ID: References: <458c04d8-d189-4a26-729a-bb1d1d751534@cisco.com> <7741efa7-a3f8-62a1-ba52-613883164643@cisco.com> <20181024140214.GG30128@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20181024140214.GG30128@redhat.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Oleg Nesterov Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Peter Zijlstra , Arnd Bergmann , "Eric W. Biederman" , Khalid Aziz , Kate Stewart , Helge Deller , Greg Kroah-Hartman , Al Viro , Andrew Morton , Christian Brauner , Catalin Marinas , Will Deacon , Dave Martin , Mauro Carvalho Chehab , Michal Hocko , Rik van Riel List-Id: linux-arch.vger.kernel.org Hi, Oleg: On 10/24/18 7:02 AM, Oleg Nesterov wrote: > On 10/23, Enke Chen wrote: >> >> --- a/fs/coredump.c >> +++ b/fs/coredump.c >> @@ -590,6 +590,12 @@ void do_coredump(const kernel_siginfo_t *siginfo) >> if (retval < 0) >> goto fail_creds; >> >> + /* >> + * Send the pre-coredump signal to the parent if requested. >> + */ >> + do_notify_parent_predump(); >> + cond_resched(); > > I am still not sure cond_resched() makes any sense here... > >> @@ -1553,6 +1553,9 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) >> tty_audit_fork(sig); >> sched_autogroup_fork(sig); >> >> + /* Clear the pre-coredump signal for the child */ >> + sig->predump_signal = 0; > > No need, copy_signal() does zalloc(). > Removed. > >> +void do_notify_parent_predump(void) >> +{ >> + struct sighand_struct *sighand; >> + struct kernel_siginfo info; >> + struct task_struct *parent; >> + unsigned long flags; >> + int sig; >> + >> + read_lock(&tasklist_lock); >> + parent = current->parent; >> + sig = parent->signal->predump_signal; >> + if (sig != 0) { >> + clear_siginfo(&info); >> + info.si_pid = task_tgid_vnr(current); >> + info.si_signo = sig; >> + if (sig == SIGCHLD) >> + info.si_code = CLD_PREDUMP; >> + >> + sighand = parent->sighand; >> + spin_lock_irqsave(&sighand->siglock, flags); >> + __group_send_sig_info(sig, &info, parent); >> + spin_unlock_irqrestore(&sighand->siglock, flags); > > You can just use do_send_sig_info() and remove sighand/flags/spin_lock_irqsave. Ok. > > Perhaps the "likely" predump_signal==0 check at the start makes sense to avoid > read_lock(tasklist). I am not sure if we should/need to deviate from the convention (locking before access the parent). In any case it may not matter as the coredump is in the exceptional code flow. > > And I'd suggest to move it into coredump.c and make it static. It won't have > another user. Ok. Thanks. -- Enke From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from alln-iport-2.cisco.com ([173.37.142.89]:37932 "EHLO alln-iport-2.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726019AbeJYGcV (ORCPT ); Thu, 25 Oct 2018 02:32:21 -0400 Subject: Re: [PATCH v3] kernel/signal: Signal-based pre-coredump notification References: <458c04d8-d189-4a26-729a-bb1d1d751534@cisco.com> <7741efa7-a3f8-62a1-ba52-613883164643@cisco.com> <20181024140214.GG30128@redhat.com> From: Enke Chen Message-ID: Date: Wed, 24 Oct 2018 15:02:29 -0700 MIME-Version: 1.0 In-Reply-To: <20181024140214.GG30128@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Oleg Nesterov Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Peter Zijlstra , Arnd Bergmann , "Eric W. Biederman" , Khalid Aziz , Kate Stewart , Helge Deller , Greg Kroah-Hartman , Al Viro , Andrew Morton , Christian Brauner , Catalin Marinas , Will Deacon , Dave Martin , Mauro Carvalho Chehab , Michal Hocko , Rik van Riel , "Kirill A. Shutemov" , Roman Gushchin , Marcos Paulo de Souza , Dominik Brodowski , Cyrill Gorcunov , Yang Shi , Jann Horn , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, "Victor Kamensky (kamensky)" , xe-linux-external@cisco.com, Stefan Strogin , Enke Chen Message-ID: <20181024220229.crwmxTRs_DAkx2k1Bp-IOSjAMvVasaaepKCaRBI41-E@z> Hi, Oleg: On 10/24/18 7:02 AM, Oleg Nesterov wrote: > On 10/23, Enke Chen wrote: >> >> --- a/fs/coredump.c >> +++ b/fs/coredump.c >> @@ -590,6 +590,12 @@ void do_coredump(const kernel_siginfo_t *siginfo) >> if (retval < 0) >> goto fail_creds; >> >> + /* >> + * Send the pre-coredump signal to the parent if requested. >> + */ >> + do_notify_parent_predump(); >> + cond_resched(); > > I am still not sure cond_resched() makes any sense here... > >> @@ -1553,6 +1553,9 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) >> tty_audit_fork(sig); >> sched_autogroup_fork(sig); >> >> + /* Clear the pre-coredump signal for the child */ >> + sig->predump_signal = 0; > > No need, copy_signal() does zalloc(). > Removed. > >> +void do_notify_parent_predump(void) >> +{ >> + struct sighand_struct *sighand; >> + struct kernel_siginfo info; >> + struct task_struct *parent; >> + unsigned long flags; >> + int sig; >> + >> + read_lock(&tasklist_lock); >> + parent = current->parent; >> + sig = parent->signal->predump_signal; >> + if (sig != 0) { >> + clear_siginfo(&info); >> + info.si_pid = task_tgid_vnr(current); >> + info.si_signo = sig; >> + if (sig == SIGCHLD) >> + info.si_code = CLD_PREDUMP; >> + >> + sighand = parent->sighand; >> + spin_lock_irqsave(&sighand->siglock, flags); >> + __group_send_sig_info(sig, &info, parent); >> + spin_unlock_irqrestore(&sighand->siglock, flags); > > You can just use do_send_sig_info() and remove sighand/flags/spin_lock_irqsave. Ok. > > Perhaps the "likely" predump_signal==0 check at the start makes sense to avoid > read_lock(tasklist). I am not sure if we should/need to deviate from the convention (locking before access the parent). In any case it may not matter as the coredump is in the exceptional code flow. > > And I'd suggest to move it into coredump.c and make it static. It won't have > another user. Ok. Thanks. -- Enke