From patchwork Tue Dec 6 18:09:24 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: xinhui X-Patchwork-Id: 703141 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [103.22.144.68]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3tY2Hc0ylRz9vcG for ; Wed, 7 Dec 2016 00:18:04 +1100 (AEDT) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 3tY2Hc01fZzDw7w for ; Wed, 7 Dec 2016 00:18:04 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3tY29x4y2CzDvkS for ; Wed, 7 Dec 2016 00:13:09 +1100 (AEDT) Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uB6D5V8K121233 for ; Tue, 6 Dec 2016 08:13:07 -0500 Received: from e23smtp03.au.ibm.com (e23smtp03.au.ibm.com [202.81.31.145]) by mx0a-001b2d01.pphosted.com with ESMTP id 275rkx1sm8-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 06 Dec 2016 08:13:06 -0500 Received: from localhost by e23smtp03.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 6 Dec 2016 23:13:04 +1000 Received: from d23dlp02.au.ibm.com (202.81.31.213) by e23smtp03.au.ibm.com (202.81.31.209) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Tue, 6 Dec 2016 23:13:03 +1000 Received: from d23relay06.au.ibm.com (d23relay06.au.ibm.com [9.185.63.219]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id 7A6992BB005B for ; Wed, 7 Dec 2016 00:13:02 +1100 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay06.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id uB6DD2gn53739570 for ; Wed, 7 Dec 2016 00:13:02 +1100 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id uB6DD1dS000465 for ; Wed, 7 Dec 2016 00:13:02 +1100 Received: from ltcalpine2-lp13.aus.stglabs.ibm.com (ltcalpine2-lp13.aus.stglabs.ibm.com [9.40.195.196]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id uB6DCnYw032667; Wed, 7 Dec 2016 00:12:59 +1100 From: Pan Xinhui To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: [PATCH v9 3/6] powerpc: lib/locks.c: Add cpu yield/wake helper function Date: Tue, 6 Dec 2016 13:09:24 -0500 X-Mailer: git-send-email 2.4.11 In-Reply-To: <1481047767-60255-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> References: <1481047767-60255-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16120613-0008-0000-0000-000000EE0BEA X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16120613-0009-0000-0000-000008A6516F Message-Id: <1481047767-60255-4-git-send-email-xinhui.pan@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2016-12-06_07:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=1 spamscore=1 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609300000 definitions=main-1612060208 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: xinhui.pan@linux.vnet.ibm.com, peterz@infradead.org, boqun.feng@gmail.com, virtualization@lists.linux-foundation.org, mingo@redhat.com, paulus@samba.org, longman@redhat.com, paulmck@linux.vnet.ibm.com Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Add two corresponding helper functions to support pv-qspinlock. For normal use, __spin_yield_cpu will confer current vcpu slices to the target vcpu(say, a lock holder). If target vcpu is not specified or it is in running state, such conferging to lpar happens or not depends. Because hcall itself will introduce latency and a little overhead. And we do NOT want to suffer any latency on some cases, e.g. in interrupt handler. The second parameter *confer* can indicate such case. __spin_wake_cpu is simpiler, it will wake up one vcpu regardless of its current vcpu state. Signed-off-by: Pan Xinhui --- arch/powerpc/include/asm/spinlock.h | 4 +++ arch/powerpc/lib/locks.c | 57 +++++++++++++++++++++++++++++++++++++ 2 files changed, 61 insertions(+) diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h index 954099e..6426bd5 100644 --- a/arch/powerpc/include/asm/spinlock.h +++ b/arch/powerpc/include/asm/spinlock.h @@ -64,9 +64,13 @@ static inline bool vcpu_is_preempted(int cpu) /* We only yield to the hypervisor if we are in shared processor mode */ #define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr)) extern void __spin_yield(arch_spinlock_t *lock); +extern void __spin_yield_cpu(int cpu, int confer); +extern void __spin_wake_cpu(int cpu); extern void __rw_yield(arch_rwlock_t *lock); #else /* SPLPAR */ #define __spin_yield(x) barrier() +#define __spin_yield_cpu(x, y) barrier() +#define __spin_wake_cpu(x) barrier() #define __rw_yield(x) barrier() #define SHARED_PROCESSOR 0 #endif diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c index 8f6dbb0..dff0bfa 100644 --- a/arch/powerpc/lib/locks.c +++ b/arch/powerpc/lib/locks.c @@ -23,6 +23,63 @@ #include #include +/* + * confer our slices to a specified cpu and return. If it is in running state + * or cpu is -1, then we will check confer. If confer is NULL, we will return + * otherwise we confer our slices to lpar. + */ +void __spin_yield_cpu(int cpu, int confer) +{ + unsigned int yield_count; + + if (cpu == -1) + goto yield_to_lpar; + + BUG_ON(cpu >= nr_cpu_ids); + yield_count = be32_to_cpu(lppaca_of(cpu).yield_count); + + /* if cpu is running, confer slices to lpar conditionally*/ + if ((yield_count & 1) == 0) + goto yield_to_lpar; + + plpar_hcall_norets(H_CONFER, + get_hard_smp_processor_id(cpu), yield_count); + return; + +yield_to_lpar: + if (confer) + plpar_hcall_norets(H_CONFER, -1, 0); +} +EXPORT_SYMBOL_GPL(__spin_yield_cpu); + +void __spin_wake_cpu(int cpu) +{ + BUG_ON(cpu >= nr_cpu_ids); + /* + * NOTE: we should always do this hcall regardless of + * the yield_count of the holder_cpu. + * as thers might be a case like below; + * CPU 1 CPU 2 + * yielded = true + * if (yielded) + * __spin_wake_cpu() + * __spin_yield_cpu() + * + * So we might lose a wake if we check the yield_count and + * return directly if the holder_cpu is running. + * IOW. do NOT code like below. + * yield_count = be32_to_cpu(lppaca_of(cpu).yield_count); + * if ((yield_count & 1) == 0) + * return; + * + * a PROD hcall marks the target_cpu proded, which cause the next cede + * or confer called on the target_cpu invalid. + */ + plpar_hcall_norets(H_PROD, + get_hard_smp_processor_id(cpu)); +} +EXPORT_SYMBOL_GPL(__spin_wake_cpu); + #ifndef CONFIG_QUEUED_SPINLOCKS void __spin_yield(arch_spinlock_t *lock) {