From nobody Mon Feb 9 09:16:21 2026 Delivered-To: importer@patchew.org Received-SPF: none (zoho.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; spf=none (zoho.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org ARC-Seal: i=1; a=rsa-sha256; t=1557125913; cv=none; d=zoho.com; s=zohoarc; b=okQN99mODa+xIPMNK3iL7TvYegZTYT5Kifkf9KDUdXGb0qLWLY+slNdqaEsF9G8W2zcXAz5Ch4jyVCvP3xQgWpezROvcbyy6HLX+90DdbXlCcA2WN/RvBTPeA3WUqcilABEr+cYBEgBDiyERUOEsLlWbJOZMosZBbc2b/jB0FE4= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1557125913; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To:ARC-Authentication-Results; bh=YZIxMbAVoCtEoGI+SfTSZvac2sRhXAp/q/j73/h7aI0=; b=PFHrv/jzh2FpNj0coOwo/Jlc7gpeIugSZjo+LqkNI5eyNfx0FnMHXijdNwv6hEX/euZxmdEZTR4jccfIGrI/CbS24fE68EpAKz/E2bC1uvw8tsVSDPHAKYuZALmAjiJAZMohu6XPtCmhK1ZoaEUPDobgC9dXJOrb97CFjOerrh0= ARC-Authentication-Results: i=1; mx.zoho.com; spf=none (zoho.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1557125913479854.4652365385314; Sun, 5 May 2019 23:58:33 -0700 (PDT) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1hNXZ9-0003De-Am; Mon, 06 May 2019 06:57:35 +0000 Received: from us1-rack-dfw2.inumbo.com ([104.130.134.6]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1hNXYn-0002Kn-Tu for xen-devel@lists.xenproject.org; Mon, 06 May 2019 06:57:13 +0000 Received: from mx1.suse.de (unknown [195.135.220.15]) by us1-rack-dfw2.inumbo.com (Halon) with ESMTPS id 27acffe4-6fcc-11e9-843c-bc764e045a96; Mon, 06 May 2019 06:57:04 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 56C17AF41; Mon, 6 May 2019 06:57:00 +0000 (UTC) X-Inumbo-ID: 27acffe4-6fcc-11e9-843c-bc764e045a96 X-Virus-Scanned: by amavisd-new at test-mx.suse.de From: Juergen Gross To: xen-devel@lists.xenproject.org Date: Mon, 6 May 2019 08:56:42 +0200 Message-Id: <20190506065644.7415-44-jgross@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20190506065644.7415-1-jgross@suse.com> References: <20190506065644.7415-1-jgross@suse.com> Subject: [Xen-devel] [PATCH RFC V2 43/45] xen/sched: make vcpu_wake() and vcpu_sleep() core scheduling aware X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Tim Deegan , Stefano Stabellini , Wei Liu , Konrad Rzeszutek Wilk , George Dunlap , Andrew Cooper , Ian Jackson , Dario Faggioli , Julien Grall , Jan Beulich MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" vcpu_wake() and vcpu_sleep() need to be made core scheduling aware: they might need to switch a single vcpu of an already scheduled item between running and not running. Especially when vcpu_sleep() for a vcpu is being called by a vcpu of the same scheduling item special care must be taken in order to avoid a deadlock: the vcpu to be put asleep must be forced through a context switch without doing so for the calling vcpu. For this purpose add a vcpu flag handled in sched_slave() and in sched_wait_rendezvous_in() allowing a vcpu of the currently running item to switch state at a higher priority than a normal schedule event. Use the same mechanism when waking up a vcpu of a currently active item. While at it make vcpu_sleep_nosync_locked() static as it is used in schedule.c only. Signed-off-by: Juergen Gross --- RFC V2: add vcpu_sleep() handling and force_context_switch flag --- xen/common/schedule.c | 144 ++++++++++++++++++++++++++++++++++++++++-= ---- xen/include/xen/sched-if.h | 9 ++- xen/include/xen/sched.h | 2 + 3 files changed, 136 insertions(+), 19 deletions(-) diff --git a/xen/common/schedule.c b/xen/common/schedule.c index 788ecc9e81..49ed2b5900 100644 --- a/xen/common/schedule.c +++ b/xen/common/schedule.c @@ -79,21 +79,21 @@ extern const struct scheduler *__start_schedulers_array= [], *__end_schedulers_arr =20 static struct scheduler __read_mostly ops; =20 -static inline struct vcpu *sched_item2vcpu_cpu(struct sched_item *item, - unsigned int cpu) +static inline struct vcpu *item2vcpu_cpu(struct sched_item *item, + unsigned int cpu) { unsigned int idx =3D item->item_id + per_cpu(sched_res_idx, cpu); const struct domain *d =3D item->domain; - struct vcpu *v; =20 - if ( idx < d->max_vcpus && d->vcpu[idx] ) - { - v =3D d->vcpu[idx]; - if ( v->new_state =3D=3D RUNSTATE_running ) - return v; - } + return (idx < d->max_vcpus && d->vcpu[idx]) ? d->vcpu[idx] : NULL; +} =20 - return idle_vcpu[cpu]; +static inline struct vcpu *sched_item2vcpu_cpu(struct sched_item *item, + unsigned int cpu) +{ + struct vcpu *v =3D item2vcpu_cpu(item, cpu); + + return (v && v->new_state =3D=3D RUNSTATE_running) ? v : idle_vcpu[cpu= ]; } =20 static inline struct scheduler *dom_scheduler(const struct domain *d) @@ -644,8 +644,10 @@ void sched_destroy_domain(struct domain *d) } } =20 -void vcpu_sleep_nosync_locked(struct vcpu *v) +static void vcpu_sleep_nosync_locked(struct vcpu *v) { + struct sched_item *item =3D v->sched_item; + ASSERT(spin_is_locked(per_cpu(sched_res, v->processor)->schedule_lock)= ); =20 if ( likely(!vcpu_runnable(v)) ) @@ -653,7 +655,14 @@ void vcpu_sleep_nosync_locked(struct vcpu *v) if ( v->runstate.state =3D=3D RUNSTATE_runnable ) vcpu_runstate_change(v, RUNSTATE_offline, NOW()); =20 - sched_sleep(vcpu_scheduler(v), v->sched_item); + if ( likely(!item_runnable(item)) ) + sched_sleep(vcpu_scheduler(v), item); + else if ( item_running(item) > 1 && v->is_running && + !v->force_context_switch ) + { + v->force_context_switch =3D true; + cpu_raise_softirq(v->processor, SCHED_SLAVE_SOFTIRQ); + } } } =20 @@ -685,16 +694,22 @@ void vcpu_wake(struct vcpu *v) { unsigned long flags; spinlock_t *lock; + struct sched_item *item =3D v->sched_item; =20 TRACE_2D(TRC_SCHED_WAKE, v->domain->domain_id, v->vcpu_id); =20 - lock =3D item_schedule_lock_irqsave(v->sched_item, &flags); + lock =3D item_schedule_lock_irqsave(item, &flags); =20 if ( likely(vcpu_runnable(v)) ) { if ( v->runstate.state >=3D RUNSTATE_blocked ) vcpu_runstate_change(v, RUNSTATE_runnable, NOW()); - sched_wake(vcpu_scheduler(v), v->sched_item); + sched_wake(vcpu_scheduler(v), item); + if ( item->is_running && !v->is_running && !v->force_context_switc= h ) + { + v->force_context_switch =3D true; + cpu_raise_softirq(v->processor, SCHED_SLAVE_SOFTIRQ); + } } else if ( !(v->pause_flags & VPF_blocked) ) { @@ -702,7 +717,7 @@ void vcpu_wake(struct vcpu *v) vcpu_runstate_change(v, RUNSTATE_offline, NOW()); } =20 - item_schedule_unlock_irqrestore(lock, flags, v->sched_item); + item_schedule_unlock_irqrestore(lock, flags, item); } =20 void vcpu_unblock(struct vcpu *v) @@ -1835,6 +1850,61 @@ static void sched_context_switch(struct vcpu *vprev,= struct vcpu *vnext, context_switch(vprev, vnext); } =20 +/* + * Force a context switch of a single vcpu of an item. + * Might be called either if a vcpu of an already running item is woken up + * or if a vcpu of a running item is put asleep with other vcpus of the sa= me + * item still running. + */ +static struct vcpu *sched_force_context_switch(struct vcpu *vprev, + struct vcpu *v, + int cpu, s_time_t now) +{ + v->force_context_switch =3D false; + + if ( vcpu_runnable(v) =3D=3D v->is_running ) + return NULL; + + if ( vcpu_runnable(v) ) + { + if ( is_idle_vcpu(vprev) ) + { + vcpu_runstate_change(vprev, RUNSTATE_runnable, now); + vprev->sched_item =3D this_cpu(sched_res)->sched_item_idle; + } + vcpu_runstate_change(v, RUNSTATE_running, now); + } + else + { + /* Make sure not to switch last vcpu of an item away. */ + if ( item_running(v->sched_item) =3D=3D 1 ) + return NULL; + + vcpu_runstate_change(v, vcpu_runstate_blocked(v), now); + v =3D sched_item2vcpu_cpu(vprev->sched_item, cpu); + if ( v !=3D vprev ) + { + if ( is_idle_vcpu(vprev) ) + { + vcpu_runstate_change(vprev, RUNSTATE_runnable, now); + vprev->sched_item =3D this_cpu(sched_res)->sched_item_idle; + } + else + { + v->sched_item =3D vprev->sched_item; + vcpu_runstate_change(v, RUNSTATE_running, now); + } + } + } + + v->is_running =3D 1; + + /* Make sure not to loose another slave call. */ + raise_softirq(SCHED_SLAVE_SOFTIRQ); + + return v; +} + /* * Rendezvous before taking a scheduling decision. * Called with schedule lock held, so all accesses to the rendezvous count= er @@ -1850,6 +1920,7 @@ static struct sched_item *sched_wait_rendezvous_in(st= ruct sched_item *prev, s_time_t now) { struct sched_item *next; + struct vcpu *v; =20 if ( !--prev->rendezvous_in_cnt ) { @@ -1858,8 +1929,28 @@ static struct sched_item *sched_wait_rendezvous_in(s= truct sched_item *prev, return next; } =20 + v =3D item2vcpu_cpu(prev, cpu); while ( prev->rendezvous_in_cnt ) { + if ( v && v->force_context_switch ) + { + struct vcpu *vprev =3D current; + + v =3D sched_force_context_switch(vprev, v, cpu, now); + + if ( v ) + { + /* We'll come back another time, so adjust rendezvous_in_c= nt. */ + prev->rendezvous_in_cnt++; + + pcpu_schedule_unlock_irq(lock, cpu); + + sched_context_switch(vprev, v, false, now); + } + + v =3D item2vcpu_cpu(prev, cpu); + } + pcpu_schedule_unlock_irq(lock, cpu); cpu_relax(); pcpu_schedule_lock_irq(cpu); @@ -1870,10 +1961,11 @@ static struct sched_item *sched_wait_rendezvous_in(= struct sched_item *prev, =20 static void sched_slave(void) { - struct vcpu *vprev =3D current; + struct vcpu *v, *vprev =3D current; struct sched_item *prev =3D vprev->sched_item, *next; s_time_t now; spinlock_t *lock; + bool do_softirq =3D false; int cpu =3D smp_processor_id(); =20 ASSERT_NOT_IN_ATOMIC(); @@ -1882,9 +1974,29 @@ static void sched_slave(void) =20 now =3D NOW(); =20 + v =3D item2vcpu_cpu(prev, cpu); + if ( v && v->force_context_switch ) + { + v =3D sched_force_context_switch(vprev, v, cpu, now); + + if ( v ) + { + pcpu_schedule_unlock_irq(lock, cpu); + + sched_context_switch(vprev, v, false, now); + } + + do_softirq =3D true; + } + if ( !prev->rendezvous_in_cnt ) { pcpu_schedule_unlock_irq(lock, cpu); + + /* Check for failed forced context switch. */ + if ( do_softirq ) + raise_softirq(SCHEDULE_SOFTIRQ); + return; } =20 diff --git a/xen/include/xen/sched-if.h b/xen/include/xen/sched-if.h index 8981d41629..f16d81ab4a 100644 --- a/xen/include/xen/sched-if.h +++ b/xen/include/xen/sched-if.h @@ -75,6 +75,11 @@ static inline bool item_runnable(const struct sched_item= *item) return false; } =20 +static inline int vcpu_runstate_blocked(struct vcpu *v) +{ + return (v->pause_flags & VPF_blocked) ? RUNSTATE_blocked : RUNSTATE_of= fline; +} + static inline bool item_runnable_state(const struct sched_item *item) { struct vcpu *v; @@ -84,9 +89,7 @@ static inline bool item_runnable_state(const struct sched= _item *item) { runnable =3D vcpu_runnable(v); =20 - v->new_state =3D runnable ? RUNSTATE_running - : (v->pause_flags & VPF_blocked) - ? RUNSTATE_blocked : RUNSTATE_offline; + v->new_state =3D runnable ? RUNSTATE_running : vcpu_runstate_block= ed(v); =20 if ( runnable ) ret =3D true; diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h index b6a2fe28cc..5629602de5 100644 --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -186,6 +186,8 @@ struct vcpu bool is_running; /* VCPU should wake fast (do not deep sleep the CPU). */ bool is_urgent; + /* VCPU must context_switch without scheduling item. */ + bool force_context_switch; =20 #ifdef VCPU_TRAP_LAST #define VCPU_TRAP_NONE 0 --=20 2.16.4 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel