From nobody Tue Nov 11 08:28:56 2025 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=1569820984; cv=none; d=zoho.com; s=zohoarc; b=ahHA0GHznhc1p7lNyV3COzUh2L/JVco9z2vFuaE/y3lmQ2NVIWqT6G7/hbZ+sC9o88by8hZsFltBCrL2wlNLqnJDoh+U6bRS88X8lDAJh5zv/p0bdiuSBqBNqPk7xpMBfaZTNJyGG1qlaPE70hrjSAzKK9J4SxfTqdhRjd6Onek= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1569820984; 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=og2+WvZDQ4RqPSrEtkOiT8IQ5acIcqX73rcimHVOAv8=; b=HJfM1suwfwVcbknuuXJpteAQAhQIMiUhab3iVHdtXCGK2pvSZ4KmZbmAqAxYEJf3coba0lbzaHg8FFOoVeC5F7sK2F/a0V0AMTltoOWcgTSRBPVL4I3Y/+e6KwxGR+q0IgkfOZBE9MlL2ON5y+BzIGpyAdFLFxtgE8oZuZYpPAs= 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 1569820984931115.81015026702198; Sun, 29 Sep 2019 22:23:04 -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 1iEo8L-00027h-Mp; Mon, 30 Sep 2019 05:22:05 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1iEo8K-00026s-B8 for xen-devel@lists.xenproject.org; Mon, 30 Sep 2019 05:22:04 +0000 Received: from mx1.suse.de (unknown [195.135.220.15]) by localhost (Halon) with ESMTPS id 302df988-e342-11e9-8628-bc764e2007e4; Mon, 30 Sep 2019 05:21:43 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 114CDB089; Mon, 30 Sep 2019 05:21:41 +0000 (UTC) X-Inumbo-ID: 302df988-e342-11e9-8628-bc764e2007e4 X-Virus-Scanned: by amavisd-new at test-mx.suse.de From: Juergen Gross To: xen-devel@lists.xenproject.org Date: Mon, 30 Sep 2019 07:21:24 +0200 Message-Id: <20190930052135.11257-9-jgross@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20190930052135.11257-1-jgross@suse.com> References: <20190930052135.11257-1-jgross@suse.com> Subject: [Xen-devel] [PATCH v5 08/19] 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 unit between running and not running. Especially when vcpu_sleep() for a vcpu is being called by a vcpu of the same scheduling unit 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 unit 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 unit. While at it make vcpu_sleep_nosync_locked() static as it is used in schedule.c only. Signed-off-by: Juergen Gross Reviewed-by: Dario Faggioli --- RFC V2: add vcpu_sleep() handling and force_context_switch flag V2: fix runstate change in sched_force_context_switch() V4: - use unit_scheduler() where appropriate (Jan Beulich) - make cpu parameter unsigned int (Jan Beulich) - comments (Jan Beulich) - use true instead 1 for setting bool (Jan Beulich) - const parameter (Jan Beulich) V5: - add comments (Dario Faggioli) --- xen/common/schedule.c | 134 +++++++++++++++++++++++++++++++++++++++++= ++-- xen/include/xen/sched-if.h | 9 ++- xen/include/xen/sched.h | 2 + 3 files changed, 136 insertions(+), 9 deletions(-) diff --git a/xen/common/schedule.c b/xen/common/schedule.c index b4c4b04ebe..9442be1c83 100644 --- a/xen/common/schedule.c +++ b/xen/common/schedule.c @@ -751,8 +751,10 @@ 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_unit *unit =3D v->sched_unit; + ASSERT(spin_is_locked(get_sched_res(v->processor)->schedule_lock)); =20 if ( likely(!vcpu_runnable(v)) ) @@ -760,7 +762,15 @@ 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_unit); + /* Only put unit to sleep in case all vcpus are not runnable. */ + if ( likely(!unit_runnable(unit)) ) + sched_sleep(unit_scheduler(unit), unit); + else if ( unit_running(unit) > 1 && v->is_running && + !v->force_context_switch ) + { + v->force_context_switch =3D true; + cpu_raise_softirq(v->processor, SCHED_SLAVE_SOFTIRQ); + } } } =20 @@ -792,16 +802,27 @@ void vcpu_wake(struct vcpu *v) { unsigned long flags; spinlock_t *lock; + struct sched_unit *unit =3D v->sched_unit; =20 TRACE_2D(TRC_SCHED_WAKE, v->domain->domain_id, v->vcpu_id); =20 - lock =3D unit_schedule_lock_irqsave(v->sched_unit, &flags); + lock =3D unit_schedule_lock_irqsave(unit, &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_unit); + /* + * Call sched_wake() unconditionally, even if unit is running alre= ady. + * We might have not been de-scheduled after vcpu_sleep_nosync_loc= ked() + * and are now to be woken up again. + */ + sched_wake(unit_scheduler(unit), unit); + if ( unit->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) ) { @@ -809,7 +830,7 @@ void vcpu_wake(struct vcpu *v) vcpu_runstate_change(v, RUNSTATE_offline, NOW()); } =20 - unit_schedule_unlock_irqrestore(lock, flags, v->sched_unit); + unit_schedule_unlock_irqrestore(lock, flags, unit); } =20 void vcpu_unblock(struct vcpu *v) @@ -2027,6 +2048,65 @@ 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 unit. + * Might be called either if a vcpu of an already running unit is woken up + * or if a vcpu of a running unit is put asleep with other vcpus of the sa= me + * unit still running. + * Returns either NULL if v is already in the correct state or the vcpu to + * run next. + */ +static struct vcpu *sched_force_context_switch(struct vcpu *vprev, + struct vcpu *v, + unsigned 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_unit =3D get_sched_res(cpu)->sched_unit_idle; + } + vcpu_runstate_change(v, RUNSTATE_running, now); + } + else + { + /* Make sure not to switch last vcpu of an unit away. */ + if ( unit_running(v->sched_unit) =3D=3D 1 ) + return NULL; + + v->new_state =3D vcpu_runstate_blocked(v); + vcpu_runstate_change(v, v->new_state, now); + v =3D sched_unit2vcpu_cpu(vprev->sched_unit, cpu); + if ( v !=3D vprev ) + { + if ( is_idle_vcpu(vprev) ) + { + vcpu_runstate_change(vprev, RUNSTATE_runnable, now); + vprev->sched_unit =3D get_sched_res(cpu)->sched_unit_idle; + } + else + { + v->sched_unit =3D vprev->sched_unit; + vcpu_runstate_change(v, RUNSTATE_running, now); + } + } + } + + /* This vcpu will be switched to. */ + v->is_running =3D true; + + /* 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 @@ -2042,6 +2122,7 @@ static struct sched_unit *sched_wait_rendezvous_in(st= ruct sched_unit *prev, s_time_t now) { struct sched_unit *next; + struct vcpu *v; =20 if ( !--prev->rendezvous_in_cnt ) { @@ -2050,8 +2131,28 @@ static struct sched_unit *sched_wait_rendezvous_in(s= truct sched_unit *prev, return next; } =20 + v =3D unit2vcpu_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++; + atomic_set(&prev->rendezvous_out_cnt, 0); + + pcpu_schedule_unlock_irq(*lock, cpu); + + sched_context_switch(vprev, v, false, now); + } + + v =3D unit2vcpu_cpu(prev, cpu); + } /* * Coming from idle might need to do tasklet work. * In order to avoid deadlocks we can't do that here, but have to @@ -2086,10 +2187,11 @@ static struct sched_unit *sched_wait_rendezvous_in(= struct sched_unit *prev, =20 static void sched_slave(void) { - struct vcpu *vprev =3D current; + struct vcpu *v, *vprev =3D current; struct sched_unit *prev =3D vprev->sched_unit, *next; s_time_t now; spinlock_t *lock; + bool do_softirq =3D false; unsigned int cpu =3D smp_processor_id(); =20 ASSERT_NOT_IN_ATOMIC(); @@ -2098,9 +2200,29 @@ static void sched_slave(void) =20 now =3D NOW(); =20 + v =3D unit2vcpu_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 41a1083a08..021c1d7c2c 100644 --- a/xen/include/xen/sched-if.h +++ b/xen/include/xen/sched-if.h @@ -102,6 +102,11 @@ static inline bool unit_runnable(const struct sched_un= it *unit) return false; } =20 +static inline int vcpu_runstate_blocked(const struct vcpu *v) +{ + return (v->pause_flags & VPF_blocked) ? RUNSTATE_blocked : RUNSTATE_of= fline; +} + /* * Returns whether a sched_unit is runnable and sets new_state for each of= its * vcpus. It is mandatory to determine the new runstate for all vcpus of a= unit @@ -121,9 +126,7 @@ static inline bool unit_runnable_state(const struct sch= ed_unit *unit) { 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 ce4329db72..f97303668a 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 unit. */ + 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