From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e17.ny.us.ibm.com (e17.ny.us.ibm.com [129.33.205.207]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id ECB101A0601 for ; Wed, 20 May 2015 05:00:34 +1000 (AEST) Received: from /spool/local by e17.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 19 May 2015 15:00:31 -0400 Received: from b01cxnp23034.gho.pok.ibm.com (b01cxnp23034.gho.pok.ibm.com [9.57.198.29]) by d01dlp03.pok.ibm.com (Postfix) with ESMTP id B4501C90045 for ; Tue, 19 May 2015 14:51:36 -0400 (EDT) Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by b01cxnp23034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t4JJ0S5i60883014 for ; Tue, 19 May 2015 19:00:28 GMT Received: from d01av03.pok.ibm.com (localhost [127.0.0.1]) by d01av03.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t4JJ0R2p009015 for ; Tue, 19 May 2015 15:00:28 -0400 From: "Shreyas B. Prabhu" To: mpe@ellerman.id.au Subject: [PATCH] powerpc: Make doorbell check preemption safe Date: Wed, 20 May 2015 00:30:14 +0530 Message-Id: <1432062014-9115-1-git-send-email-shreyas@linux.vnet.ibm.com> Cc: mikey@neuling.org, linux-kernel@vger.kernel.org, paulus@samba.org, "Shreyas B. Prabhu" , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Doorbell can be used to cause ipi on cpus which are sibling threads on the same core. So icp_native_cause_ipi checks if the destination cpu is a sibling thread of the current cpu and uses doorbell in such cases. But while running with CONFIG_PREEMPT=y, since this section is preemtible, we can run into issues if after we check if the destination cpu is a sibling cpu, the task gets migrated from a sibling cpu to a cpu on another core. Fix this by using get_cpu()/ put_cpu() Signed-off-by: Shreyas B. Prabhu --- arch/powerpc/sysdev/xics/icp-native.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/sysdev/xics/icp-native.c b/arch/powerpc/sysdev/xics/icp-native.c index 2fc4cf1..62fd478 100644 --- a/arch/powerpc/sysdev/xics/icp-native.c +++ b/arch/powerpc/sysdev/xics/icp-native.c @@ -147,12 +147,16 @@ static void icp_native_cause_ipi(int cpu, unsigned long data) { kvmppc_set_host_ipi(cpu, 1); #ifdef CONFIG_PPC_DOORBELL - if (cpu_has_feature(CPU_FTR_DBELL) && - (cpumask_test_cpu(cpu, cpu_sibling_mask(smp_processor_id())))) - doorbell_cause_ipi(cpu, data); - else + if (cpu_has_feature(CPU_FTR_DBELL)) { + if (cpumask_test_cpu(cpu, cpu_sibling_mask(get_cpu()))) { + doorbell_cause_ipi(cpu, data); + put_cpu(); + return; + } + put_cpu(); + } #endif - icp_native_set_qirr(cpu, IPI_PRIORITY); + icp_native_set_qirr(cpu, IPI_PRIORITY); } /* -- 1.9.3