From mboxrd@z Thu Jan 1 00:00:00 1970 From: Akio Takebe Subject: Re: hvm_set_callback_irq_level() deadlock? Date: Wed, 07 Jan 2009 19:22:29 +0900 Message-ID: <49648265.6070808@jp.fujitsu.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: xen-devel List-Id: xen-devel@lists.xenproject.org Hi, Keir Fraser wrote: > On 07/01/2009 09:41, "Akio Takebe" wrote: > >> hvm_set_callback_irq_level() and so on call vioapic_irq_positive_edge() >> before spin_unlock(&d->arch.hvm_domain.irq_lock). >> I think it cause a deadlock. >> If it is right, how should we fix them? >> What do you think? > > Doesn't vioapic_irq_positive_edge() clearly expect to be called with that > lock held? I concern about that vioapic_deliver() calls vcpu_kick(). If vcpu0 has the lock and vcpu1 cannot get lock and spin then vcpu0 sleep in another function, it may cause deadlock because vioapic_irq_positive_edge() may call vcpu_kick(). For example, the following function is OK? 1087 static void time_calibration_rendezvous(void *_r) 1088 { 1089 struct cpu_calibration *c = &this_cpu(cpu_calibration); 1090 struct calibration_rendezvous *r = _r; 1091 unsigned int total_cpus = cpus_weight(r->cpu_calibration_map); 1092 1093 if ( smp_processor_id() == 0 ) 1094 { 1095 while ( atomic_read(&r->nr_cpus) != (total_cpus - 1) ) 1096 cpu_relax(); 1097 r->master_stime = read_platform_stime(); 1098 rdtscll(r->master_tsc_stamp); 1099 mb(); /* write r->master_* /then/ signal */ 1100 atomic_inc(&r->nr_cpus); 1101 c->local_tsc_stamp = r->master_tsc_stamp; 1102 } 1103 else 1104 { 1105 atomic_inc(&r->nr_cpus); 1106 while ( atomic_read(&r->nr_cpus) != total_cpus ) 1107 cpu_relax(); 1108 mb(); /* receive signal /then/ read r->master_* */ 1109 if ( boot_cpu_has(X86_FEATURE_CONSTANT_TSC) ) 1110 wrmsrl(MSR_IA32_TSC, r->master_tsc_stamp); 1111 rdtscll(c->local_tsc_stamp); 1112 } 1113 1114 c->stime_local_stamp = get_s_time(); 1115 c->stime_master_stamp = r->master_stime; 1116 1117 raise_softirq(TIME_CALIBRATE_SOFTIRQ); 1118 } Best Regards, Akio Takebe