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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id v1sm20894872wrw.90.2019.02.11.02.53.40 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 11 Feb 2019 02:53:41 -0800 (PST) Date: Mon, 11 Feb 2019 11:53:39 +0100 From: Ingo Molnar To: Fenghua Yu Cc: Thomas Gleixner , Ingo Molnar , H Peter Anvin , Dave Hansen , Ashok Raj , Peter Zijlstra , Michael Chan , Ravi V Shankar , Ricardo Neri , linux-kernel , x86 Subject: Re: [PATCH v3 10/10] x86/split_lock: Handle #AC exception for split lock Message-ID: <20190211105339.GA40840@gmail.com> References: <1549084491-57808-1-git-send-email-fenghua.yu@intel.com> <1549084491-57808-11-git-send-email-fenghua.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1549084491-57808-11-git-send-email-fenghua.yu@intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Fenghua Yu wrote: > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -61,6 +61,7 @@ > #include > #include > #include > +#include > > #ifdef CONFIG_X86_64 > #include > @@ -292,9 +293,36 @@ DO_ERROR(X86_TRAP_OLD_MF, SIGFPE, 0, NULL, "coprocessor segment overru > DO_ERROR(X86_TRAP_TS, SIGSEGV, 0, NULL, "invalid TSS", invalid_TSS) > DO_ERROR(X86_TRAP_NP, SIGBUS, 0, NULL, "segment not present", segment_not_present) > DO_ERROR(X86_TRAP_SS, SIGBUS, 0, NULL, "stack segment", stack_segment) > -DO_ERROR(X86_TRAP_AC, SIGBUS, BUS_ADRALN, NULL, "alignment check", alignment_check) > #undef IP > > +dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code) > +{ > + unsigned int trapnr = X86_TRAP_AC; > + char str[] = "alignment check"; > + int signr = SIGBUS; > + int ret; > + > + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); > + > + if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) != > + NOTIFY_STOP) { > + /* #AC exception could be handled by split lock handler. */ > + ret = do_ac_split_lock(regs); > + if (ret) { > + cond_local_irq_enable(regs); > + > + return; > + } > + > + cond_local_irq_enable(regs); > + /* > + * If not processed by split lock handler, go to generic > + * #AC handler. > + */ > + do_trap(trapnr, signr, str, regs, error_code, BUS_ADRALN, NULL); > + } > +} Is there any experience with how frequently this signal is killing user-space processes on a modern distro? Any expectation of how frequent such SIGBUS task terminations are going to be in the field? Thanks, Ingo