From patchwork Mon Nov 9 06:41:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 11890511 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 07F93921 for ; Mon, 9 Nov 2020 06:43:05 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C33C0206C0 for ; Mon, 9 Nov 2020 06:43:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="vHcHmS9u" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C33C0206C0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.21985.48345 (Exim 4.92) (envelope-from ) id 1kc0ry-00019H-Rj; Mon, 09 Nov 2020 06:41:38 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 21985.48345; Mon, 09 Nov 2020 06:41:38 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kc0ry-000194-OA; Mon, 09 Nov 2020 06:41:38 +0000 Received: by outflank-mailman (input) for mailman id 21985; Mon, 09 Nov 2020 06:41:37 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kc0rx-00015b-HR for xen-devel@lists.xenproject.org; Mon, 09 Nov 2020 06:41:37 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 22e94c58-c6a8-4bc2-8798-f3ed3cb96c7f; Mon, 09 Nov 2020 06:41:31 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AEF18ABCC; Mon, 9 Nov 2020 06:41:30 +0000 (UTC) Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kc0rx-00015b-HR for xen-devel@lists.xenproject.org; Mon, 09 Nov 2020 06:41:37 +0000 X-Inumbo-ID: 22e94c58-c6a8-4bc2-8798-f3ed3cb96c7f Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 22e94c58-c6a8-4bc2-8798-f3ed3cb96c7f; Mon, 09 Nov 2020 06:41:31 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1604904090; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DpSBXBI2OHigxodLIbPPZp3jSMwO4fg1IhybSfwcpsI=; b=vHcHmS9uJ5nMjtGus5KwQC5iOMcryUTUzOTi7GicoBnf5dhxpv8DMsx7jhwvCZfXmQj77i h2Vfpcvhmye3DCCyUi3ffHjp0+fEPzhcAwKwcBGuhTGN8yC54o3+L9A0SMR7u1xhVL2kS7 LaxgeFlgZSfsGt1TR3pk2av2fSUQdDk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AEF18ABCC; Mon, 9 Nov 2020 06:41:30 +0000 (UTC) From: Juergen Gross To: xen-devel@lists.xenproject.org Cc: Juergen Gross , Andrew Cooper , George Dunlap , Ian Jackson , Jan Beulich , Julien Grall , Stefano Stabellini , Wei Liu , Julien Grall Subject: [PATCH v5 1/2] xen/events: access last_priority and last_vcpu_id together Date: Mon, 9 Nov 2020 07:41:27 +0100 Message-Id: <20201109064128.3908-2-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201109064128.3908-1-jgross@suse.com> References: <20201109064128.3908-1-jgross@suse.com> MIME-Version: 1.0 The queue for a fifo event is depending on the vcpu_id and the priority of the event. When sending an event it might happen the event needs to change queues and the old queue needs to be kept for keeping the links between queue elements intact. For this purpose the event channel contains last_priority and last_vcpu_id values elements for being able to identify the old queue. In order to avoid races always access last_priority and last_vcpu_id with a single atomic operation avoiding any inconsistencies. Signed-off-by: Juergen Gross Reviewed-by: Julien Grall --- xen/common/event_fifo.c | 25 +++++++++++++++++++------ xen/include/xen/sched.h | 3 +-- 2 files changed, 20 insertions(+), 8 deletions(-) diff --git a/xen/common/event_fifo.c b/xen/common/event_fifo.c index c6e58d2a1a..79090c04ca 100644 --- a/xen/common/event_fifo.c +++ b/xen/common/event_fifo.c @@ -42,6 +42,14 @@ struct evtchn_fifo_domain { unsigned int num_evtchns; }; +union evtchn_fifo_lastq { + uint32_t raw; + struct { + uint8_t last_priority; + uint16_t last_vcpu_id; + }; +}; + static inline event_word_t *evtchn_fifo_word_from_port(const struct domain *d, unsigned int port) { @@ -86,16 +94,18 @@ static struct evtchn_fifo_queue *lock_old_queue(const struct domain *d, struct vcpu *v; struct evtchn_fifo_queue *q, *old_q; unsigned int try; + union evtchn_fifo_lastq lastq; for ( try = 0; try < 3; try++ ) { - v = d->vcpu[evtchn->last_vcpu_id]; - old_q = &v->evtchn_fifo->queue[evtchn->last_priority]; + lastq.raw = read_atomic(&evtchn->fifo_lastq); + v = d->vcpu[lastq.last_vcpu_id]; + old_q = &v->evtchn_fifo->queue[lastq.last_priority]; spin_lock_irqsave(&old_q->lock, *flags); - v = d->vcpu[evtchn->last_vcpu_id]; - q = &v->evtchn_fifo->queue[evtchn->last_priority]; + v = d->vcpu[lastq.last_vcpu_id]; + q = &v->evtchn_fifo->queue[lastq.last_priority]; if ( old_q == q ) return old_q; @@ -246,8 +256,11 @@ static void evtchn_fifo_set_pending(struct vcpu *v, struct evtchn *evtchn) /* Moved to a different queue? */ if ( old_q != q ) { - evtchn->last_vcpu_id = v->vcpu_id; - evtchn->last_priority = q->priority; + union evtchn_fifo_lastq lastq = { }; + + lastq.last_vcpu_id = v->vcpu_id; + lastq.last_priority = q->priority; + write_atomic(&evtchn->fifo_lastq, lastq.raw); spin_unlock_irqrestore(&old_q->lock, flags); spin_lock_irqsave(&q->lock, flags); diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h index d8ed83f869..a298ff4df8 100644 --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -114,8 +114,7 @@ struct evtchn u16 virq; /* state == ECS_VIRQ */ } u; u8 priority; - u8 last_priority; - u16 last_vcpu_id; + u32 fifo_lastq; /* Data for fifo events identifying last queue. */ #ifdef CONFIG_XSM union { #ifdef XSM_NEED_GENERIC_EVTCHN_SSID From patchwork Mon Nov 9 06:41:28 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 11890509 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6826D6A2 for ; Mon, 9 Nov 2020 06:42:28 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 20DF0206C0 for ; Mon, 9 Nov 2020 06:42:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="l1K1Qhw2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 20DF0206C0 Authentication-Results: mail.kernel.org; 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Mon, 09 Nov 2020 06:41:36 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 953adf3f-163a-41ed-ba48-99db9d9e161a; Mon, 09 Nov 2020 06:41:31 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id ED95AABD1; Mon, 9 Nov 2020 06:41:30 +0000 (UTC) Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kc0rw-00016k-HT for xen-devel@lists.xenproject.org; Mon, 09 Nov 2020 06:41:36 +0000 X-Inumbo-ID: 953adf3f-163a-41ed-ba48-99db9d9e161a Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 953adf3f-163a-41ed-ba48-99db9d9e161a; Mon, 09 Nov 2020 06:41:31 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1604904091; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JFoT60bwaPOryKk4GbCzd9C3J92QHjrVIOHIuInzsxo=; b=l1K1Qhw2FIcvDIcn0ea80pf0jFMggmKFCvZYhE+2mVUv8cSCZUQ9Nx+9mBhBMjWm99DZRi gejAg7PQRTrhmTfvPvtHhCVAgt0RD5KPCswb/freYIP+ohOBHuxygh1EbbD37WyliHAofA LuSlOFRBce/zFs3lO2qcaFP+qR6+Zb0= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id ED95AABD1; Mon, 9 Nov 2020 06:41:30 +0000 (UTC) From: Juergen Gross To: xen-devel@lists.xenproject.org Cc: Juergen Gross , Jan Beulich , Andrew Cooper , =?utf-8?q?Roger_Pau_Monn=C3=A9?= , Wei Liu , George Dunlap , Ian Jackson , Julien Grall , Stefano Stabellini Subject: [PATCH v5 2/2] xen/evtchn: rework per event channel lock Date: Mon, 9 Nov 2020 07:41:28 +0100 Message-Id: <20201109064128.3908-3-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201109064128.3908-1-jgross@suse.com> References: <20201109064128.3908-1-jgross@suse.com> MIME-Version: 1.0 Currently the lock for a single event channel needs to be taken with interrupts off, which causes deadlocks in some cases. Rework the per event channel lock to be non-blocking for the case of sending an event and removing the need for disabling interrupts for taking the lock. The lock is needed for avoiding races between event channel state changes (creation, closing, binding) against normal operations (set pending, [un]masking, priority changes). Use a rwlock, but with some restrictions: - normal operations use read_trylock(), in case of not obtaining the lock the operation is omitted or a default state is returned - closing an event channel is using write_lock(), with ASSERT()ing that the lock is taken as writer only when the state of the event channel is either before or after the locked region appropriate (either free or unbound). Fixes: e045199c7c9c54 ("evtchn: address races with evtchn_reset()") Signed-off-by: Juergen Gross --- V4: - switch to rwlock - add ASSERT() to verify correct write_lock() usage V3: - corrected a copy-and-paste error (Jan Beulich) - corrected unlocking in two cases (Jan Beulich) - renamed evtchn_read_trylock() (Jan Beulich) - added some comments and an ASSERT() for evtchn_write_lock() - set EVENT_WRITE_LOCK_INC to INT_MIN V2: - added needed barriers Signed-off-by: Juergen Gross --- xen/arch/x86/irq.c | 6 +- xen/arch/x86/pv/shim.c | 9 +-- xen/common/event_channel.c | 144 +++++++++++++++++++++---------------- xen/include/xen/event.h | 32 ++++++--- xen/include/xen/sched.h | 5 +- 5 files changed, 116 insertions(+), 80 deletions(-) diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c index 93c4fb9a79..8d1f9a9fc6 100644 --- a/xen/arch/x86/irq.c +++ b/xen/arch/x86/irq.c @@ -2495,14 +2495,12 @@ static void dump_irqs(unsigned char key) pirq = domain_irq_to_pirq(d, irq); info = pirq_info(d, pirq); evtchn = evtchn_from_port(d, info->evtchn); - local_irq_disable(); - if ( spin_trylock(&evtchn->lock) ) + if ( evtchn_read_trylock(evtchn) ) { pending = evtchn_is_pending(d, evtchn); masked = evtchn_is_masked(d, evtchn); - spin_unlock(&evtchn->lock); + evtchn_read_unlock(evtchn); } - local_irq_enable(); printk("d%d:%3d(%c%c%c)%c", d->domain_id, pirq, "-P?"[pending], "-M?"[masked], info->masked ? 'M' : '-', diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c index 9aef7a860a..b4e83e0778 100644 --- a/xen/arch/x86/pv/shim.c +++ b/xen/arch/x86/pv/shim.c @@ -660,11 +660,12 @@ void pv_shim_inject_evtchn(unsigned int port) if ( port_is_valid(guest, port) ) { struct evtchn *chn = evtchn_from_port(guest, port); - unsigned long flags; - spin_lock_irqsave(&chn->lock, flags); - evtchn_port_set_pending(guest, chn->notify_vcpu_id, chn); - spin_unlock_irqrestore(&chn->lock, flags); + if ( evtchn_read_trylock(chn) ) + { + evtchn_port_set_pending(guest, chn->notify_vcpu_id, chn); + evtchn_read_unlock(chn); + } } } diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c index cd4a2c0501..4a6b6fc5ad 100644 --- a/xen/common/event_channel.c +++ b/xen/common/event_channel.c @@ -50,6 +50,34 @@ #define consumer_is_xen(e) (!!(e)->xen_consumer) +/* + * Lock an event channel exclusively. This is allowed only when the channel is + * free or unbound either when taking or when releasing the lock, as any + * concurrent operation on the event channel using evtchn_read_trylock() will + * just assume the event channel is free or unbound at the moment when the + * evtchn_read_trylock() returns false. + */ +static inline void evtchn_write_lock(struct evtchn *evtchn) +{ + write_lock(&evtchn->lock); + + evtchn->old_state = evtchn->state; +} + +static inline void evtchn_write_unlock(struct evtchn *evtchn) +{ + /* Enforce lock discipline. */ + ASSERT(evtchn->old_state == ECS_FREE || evtchn->old_state == ECS_UNBOUND || + evtchn->state == ECS_FREE || evtchn->state == ECS_UNBOUND); + + write_unlock(&evtchn->lock); +} + +static inline void evtchn_read_lock(struct evtchn *evtchn) +{ + read_lock(&evtchn->lock); +} + /* * The function alloc_unbound_xen_event_channel() allows an arbitrary * notifier function to be specified. However, very few unique functions @@ -133,7 +161,7 @@ static struct evtchn *alloc_evtchn_bucket(struct domain *d, unsigned int port) return NULL; } chn[i].port = port + i; - spin_lock_init(&chn[i].lock); + rwlock_init(&chn[i].lock); } return chn; } @@ -255,7 +283,6 @@ static long evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc) int port; domid_t dom = alloc->dom; long rc; - unsigned long flags; d = rcu_lock_domain_by_any_id(dom); if ( d == NULL ) @@ -271,14 +298,14 @@ static long evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc) if ( rc ) goto out; - spin_lock_irqsave(&chn->lock, flags); + evtchn_write_lock(chn); chn->state = ECS_UNBOUND; if ( (chn->u.unbound.remote_domid = alloc->remote_dom) == DOMID_SELF ) chn->u.unbound.remote_domid = current->domain->domain_id; evtchn_port_init(d, chn); - spin_unlock_irqrestore(&chn->lock, flags); + evtchn_write_unlock(chn); alloc->port = port; @@ -291,32 +318,26 @@ static long evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc) } -static unsigned long double_evtchn_lock(struct evtchn *lchn, - struct evtchn *rchn) +static void double_evtchn_lock(struct evtchn *lchn, struct evtchn *rchn) { - unsigned long flags; - if ( lchn <= rchn ) { - spin_lock_irqsave(&lchn->lock, flags); + evtchn_write_lock(lchn); if ( lchn != rchn ) - spin_lock(&rchn->lock); + evtchn_write_lock(rchn); } else { - spin_lock_irqsave(&rchn->lock, flags); - spin_lock(&lchn->lock); + evtchn_write_lock(rchn); + evtchn_write_lock(lchn); } - - return flags; } -static void double_evtchn_unlock(struct evtchn *lchn, struct evtchn *rchn, - unsigned long flags) +static void double_evtchn_unlock(struct evtchn *lchn, struct evtchn *rchn) { if ( lchn != rchn ) - spin_unlock(&lchn->lock); - spin_unlock_irqrestore(&rchn->lock, flags); + evtchn_write_unlock(lchn); + evtchn_write_unlock(rchn); } static long evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind) @@ -326,7 +347,6 @@ static long evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind) int lport, rport = bind->remote_port; domid_t rdom = bind->remote_dom; long rc; - unsigned long flags; if ( rdom == DOMID_SELF ) rdom = current->domain->domain_id; @@ -362,7 +382,7 @@ static long evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind) if ( rc ) goto out; - flags = double_evtchn_lock(lchn, rchn); + double_evtchn_lock(lchn, rchn); lchn->u.interdomain.remote_dom = rd; lchn->u.interdomain.remote_port = rport; @@ -379,7 +399,7 @@ static long evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind) */ evtchn_port_set_pending(ld, lchn->notify_vcpu_id, lchn); - double_evtchn_unlock(lchn, rchn, flags); + double_evtchn_unlock(lchn, rchn); bind->local_port = lport; @@ -402,7 +422,6 @@ int evtchn_bind_virq(evtchn_bind_virq_t *bind, evtchn_port_t port) struct domain *d = current->domain; int virq = bind->virq, vcpu = bind->vcpu; int rc = 0; - unsigned long flags; if ( (virq < 0) || (virq >= ARRAY_SIZE(v->virq_to_evtchn)) ) return -EINVAL; @@ -440,14 +459,14 @@ int evtchn_bind_virq(evtchn_bind_virq_t *bind, evtchn_port_t port) chn = evtchn_from_port(d, port); - spin_lock_irqsave(&chn->lock, flags); + evtchn_write_lock(chn); chn->state = ECS_VIRQ; chn->notify_vcpu_id = vcpu; chn->u.virq = virq; evtchn_port_init(d, chn); - spin_unlock_irqrestore(&chn->lock, flags); + evtchn_write_unlock(chn); v->virq_to_evtchn[virq] = bind->port = port; @@ -464,7 +483,6 @@ static long evtchn_bind_ipi(evtchn_bind_ipi_t *bind) struct domain *d = current->domain; int port, vcpu = bind->vcpu; long rc = 0; - unsigned long flags; if ( domain_vcpu(d, vcpu) == NULL ) return -ENOENT; @@ -476,13 +494,13 @@ static long evtchn_bind_ipi(evtchn_bind_ipi_t *bind) chn = evtchn_from_port(d, port); - spin_lock_irqsave(&chn->lock, flags); + evtchn_write_lock(chn); chn->state = ECS_IPI; chn->notify_vcpu_id = vcpu; evtchn_port_init(d, chn); - spin_unlock_irqrestore(&chn->lock, flags); + evtchn_write_unlock(chn); bind->port = port; @@ -526,7 +544,6 @@ static long evtchn_bind_pirq(evtchn_bind_pirq_t *bind) struct pirq *info; int port = 0, pirq = bind->pirq; long rc; - unsigned long flags; if ( (pirq < 0) || (pirq >= d->nr_pirqs) ) return -EINVAL; @@ -559,14 +576,14 @@ static long evtchn_bind_pirq(evtchn_bind_pirq_t *bind) goto out; } - spin_lock_irqsave(&chn->lock, flags); + evtchn_write_lock(chn); chn->state = ECS_PIRQ; chn->u.pirq.irq = pirq; link_pirq_port(port, chn, v); evtchn_port_init(d, chn); - spin_unlock_irqrestore(&chn->lock, flags); + evtchn_write_unlock(chn); bind->port = port; @@ -587,7 +604,6 @@ int evtchn_close(struct domain *d1, int port1, bool guest) struct evtchn *chn1, *chn2; int port2; long rc = 0; - unsigned long flags; again: spin_lock(&d1->event_lock); @@ -688,14 +704,14 @@ int evtchn_close(struct domain *d1, int port1, bool guest) BUG_ON(chn2->state != ECS_INTERDOMAIN); BUG_ON(chn2->u.interdomain.remote_dom != d1); - flags = double_evtchn_lock(chn1, chn2); + double_evtchn_lock(chn1, chn2); evtchn_free(d1, chn1); chn2->state = ECS_UNBOUND; chn2->u.unbound.remote_domid = d1->domain_id; - double_evtchn_unlock(chn1, chn2, flags); + double_evtchn_unlock(chn1, chn2); goto out; @@ -703,9 +719,9 @@ int evtchn_close(struct domain *d1, int port1, bool guest) BUG(); } - spin_lock_irqsave(&chn1->lock, flags); + evtchn_write_lock(chn1); evtchn_free(d1, chn1); - spin_unlock_irqrestore(&chn1->lock, flags); + evtchn_write_unlock(chn1); out: if ( d2 != NULL ) @@ -725,7 +741,6 @@ int evtchn_send(struct domain *ld, unsigned int lport) struct evtchn *lchn, *rchn; struct domain *rd; int rport, ret = 0; - unsigned long flags; if ( !port_is_valid(ld, lport) ) return -EINVAL; @@ -738,7 +753,7 @@ int evtchn_send(struct domain *ld, unsigned int lport) lchn = evtchn_from_port(ld, lport); - spin_lock_irqsave(&lchn->lock, flags); + evtchn_read_lock(lchn); /* Guest cannot send via a Xen-attached event channel. */ if ( unlikely(consumer_is_xen(lchn)) ) @@ -773,7 +788,7 @@ int evtchn_send(struct domain *ld, unsigned int lport) } out: - spin_unlock_irqrestore(&lchn->lock, flags); + evtchn_read_unlock(lchn); return ret; } @@ -806,9 +821,11 @@ void send_guest_vcpu_virq(struct vcpu *v, uint32_t virq) d = v->domain; chn = evtchn_from_port(d, port); - spin_lock(&chn->lock); - evtchn_port_set_pending(d, v->vcpu_id, chn); - spin_unlock(&chn->lock); + if ( evtchn_read_trylock(chn) ) + { + evtchn_port_set_pending(d, v->vcpu_id, chn); + evtchn_read_unlock(chn); + } out: spin_unlock_irqrestore(&v->virq_lock, flags); @@ -837,9 +854,11 @@ void send_guest_global_virq(struct domain *d, uint32_t virq) goto out; chn = evtchn_from_port(d, port); - spin_lock(&chn->lock); - evtchn_port_set_pending(d, chn->notify_vcpu_id, chn); - spin_unlock(&chn->lock); + if ( evtchn_read_trylock(chn) ) + { + evtchn_port_set_pending(d, chn->notify_vcpu_id, chn); + evtchn_read_unlock(chn); + } out: spin_unlock_irqrestore(&v->virq_lock, flags); @@ -849,7 +868,6 @@ void send_guest_pirq(struct domain *d, const struct pirq *pirq) { int port; struct evtchn *chn; - unsigned long flags; /* * PV guests: It should not be possible to race with __evtchn_close(). The @@ -864,9 +882,11 @@ void send_guest_pirq(struct domain *d, const struct pirq *pirq) } chn = evtchn_from_port(d, port); - spin_lock_irqsave(&chn->lock, flags); - evtchn_port_set_pending(d, chn->notify_vcpu_id, chn); - spin_unlock_irqrestore(&chn->lock, flags); + if ( evtchn_read_trylock(chn) ) + { + evtchn_port_set_pending(d, chn->notify_vcpu_id, chn); + evtchn_read_unlock(chn); + } } static struct domain *global_virq_handlers[NR_VIRQS] __read_mostly; @@ -1068,15 +1088,16 @@ int evtchn_unmask(unsigned int port) { struct domain *d = current->domain; struct evtchn *evtchn; - unsigned long flags; if ( unlikely(!port_is_valid(d, port)) ) return -EINVAL; evtchn = evtchn_from_port(d, port); - spin_lock_irqsave(&evtchn->lock, flags); - evtchn_port_unmask(d, evtchn); - spin_unlock_irqrestore(&evtchn->lock, flags); + if ( evtchn_read_trylock(evtchn) ) + { + evtchn_port_unmask(d, evtchn); + evtchn_read_unlock(evtchn); + } return 0; } @@ -1156,15 +1177,17 @@ static long evtchn_set_priority(const struct evtchn_set_priority *set_priority) unsigned int port = set_priority->port; struct evtchn *chn; long ret; - unsigned long flags; if ( !port_is_valid(d, port) ) return -EINVAL; chn = evtchn_from_port(d, port); - spin_lock_irqsave(&chn->lock, flags); + + evtchn_read_lock(chn); + ret = evtchn_port_set_priority(d, chn, set_priority->priority); - spin_unlock_irqrestore(&chn->lock, flags); + + evtchn_read_unlock(chn); return ret; } @@ -1332,7 +1355,6 @@ int alloc_unbound_xen_event_channel( { struct evtchn *chn; int port, rc; - unsigned long flags; spin_lock(&ld->event_lock); @@ -1345,14 +1367,14 @@ int alloc_unbound_xen_event_channel( if ( rc ) goto out; - spin_lock_irqsave(&chn->lock, flags); + evtchn_write_lock(chn); chn->state = ECS_UNBOUND; chn->xen_consumer = get_xen_consumer(notification_fn); chn->notify_vcpu_id = lvcpu; chn->u.unbound.remote_domid = remote_domid; - spin_unlock_irqrestore(&chn->lock, flags); + evtchn_write_unlock(chn); /* * Increment ->xen_evtchns /after/ ->active_evtchns. No explicit @@ -1388,7 +1410,6 @@ void notify_via_xen_event_channel(struct domain *ld, int lport) { struct evtchn *lchn, *rchn; struct domain *rd; - unsigned long flags; if ( !port_is_valid(ld, lport) ) { @@ -1403,7 +1424,8 @@ void notify_via_xen_event_channel(struct domain *ld, int lport) lchn = evtchn_from_port(ld, lport); - spin_lock_irqsave(&lchn->lock, flags); + if ( !evtchn_read_trylock(lchn) ) + return; if ( likely(lchn->state == ECS_INTERDOMAIN) ) { @@ -1413,7 +1435,7 @@ void notify_via_xen_event_channel(struct domain *ld, int lport) evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn); } - spin_unlock_irqrestore(&lchn->lock, flags); + evtchn_read_unlock(lchn); } void evtchn_check_pollers(struct domain *d, unsigned int port) diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h index 2ed4be78f6..9c84265f53 100644 --- a/xen/include/xen/event.h +++ b/xen/include/xen/event.h @@ -105,6 +105,16 @@ void notify_via_xen_event_channel(struct domain *ld, int lport); #define bucket_from_port(d, p) \ ((group_from_port(d, p))[((p) % EVTCHNS_PER_GROUP) / EVTCHNS_PER_BUCKET]) +static inline bool evtchn_read_trylock(struct evtchn *evtchn) +{ + return read_trylock(&evtchn->lock); +} + +static inline void evtchn_read_unlock(struct evtchn *evtchn) +{ + read_unlock(&evtchn->lock); +} + static inline bool_t port_is_valid(struct domain *d, unsigned int p) { if ( p >= read_atomic(&d->valid_evtchns) ) @@ -234,12 +244,13 @@ static inline bool evtchn_is_masked(const struct domain *d, static inline bool evtchn_port_is_masked(struct domain *d, evtchn_port_t port) { struct evtchn *evtchn = evtchn_from_port(d, port); - bool rc; - unsigned long flags; + bool rc = true; - spin_lock_irqsave(&evtchn->lock, flags); - rc = evtchn_is_masked(d, evtchn); - spin_unlock_irqrestore(&evtchn->lock, flags); + if ( evtchn_read_trylock(evtchn) ) + { + rc = evtchn_is_masked(d, evtchn); + evtchn_read_unlock(evtchn); + } return rc; } @@ -252,12 +263,13 @@ static inline int evtchn_port_poll(struct domain *d, evtchn_port_t port) if ( port_is_valid(d, port) ) { struct evtchn *evtchn = evtchn_from_port(d, port); - unsigned long flags; - spin_lock_irqsave(&evtchn->lock, flags); - if ( evtchn_usable(evtchn) ) - rc = evtchn_is_pending(d, evtchn); - spin_unlock_irqrestore(&evtchn->lock, flags); + if ( evtchn_read_trylock(evtchn) ) + { + if ( evtchn_usable(evtchn) ) + rc = evtchn_is_pending(d, evtchn); + evtchn_read_unlock(evtchn); + } } return rc; diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h index a298ff4df8..66d8f058be 100644 --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -85,7 +85,7 @@ extern domid_t hardware_domid; struct evtchn { - spinlock_t lock; + rwlock_t lock; #define ECS_FREE 0 /* Channel is available for use. */ #define ECS_RESERVED 1 /* Channel is reserved. */ #define ECS_UNBOUND 2 /* Channel is waiting to bind to a remote domain. */ @@ -114,6 +114,9 @@ struct evtchn u16 virq; /* state == ECS_VIRQ */ } u; u8 priority; +#ifndef NDEBUG + u8 old_state; /* State when taking lock in write mode. */ +#endif u32 fifo_lastq; /* Data for fifo events identifying last queue. */ #ifdef CONFIG_XSM union {