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Date: Thu, 30 Aug 2018 16:28:22 +0000 From: KY Srinivasan <kys@...rosoft.com> To: Dexuan Cui <decui@...rosoft.com>, "'gregkh@...uxfoundation.org'" <gregkh@...uxfoundation.org>, Stephen Hemminger <sthemmin@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com> CC: "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>, "'driverdev-devel@...uxdriverproject.org'" <driverdev-devel@...uxdriverproject.org>, "'olaf@...fle.de'" <olaf@...fle.de>, "'apw@...onical.com'" <apw@...onical.com>, "'jasowang@...hat.com'" <jasowang@...hat.com>, vkuznets <vkuznets@...hat.com>, "'marcelo.cerri@...onical.com'" <marcelo.cerri@...onical.com> Subject: RE: [PATCH] Drivers: hv: vmbus: Use raw_smp_processor_id() in vmbus_connect() > -----Original Message----- > From: Dexuan Cui > Sent: Thursday, August 23, 2018 3:31 PM > To: 'gregkh@...uxfoundation.org' <gregkh@...uxfoundation.org>; KY > Srinivasan <kys@...rosoft.com>; Stephen Hemminger > <sthemmin@...rosoft.com>; Haiyang Zhang <haiyangz@...rosoft.com> > Cc: 'linux-kernel@...r.kernel.org' <linux-kernel@...r.kernel.org>; > 'driverdev-devel@...uxdriverproject.org' <driverdev- > devel@...uxdriverproject.org>; 'olaf@...fle.de' <olaf@...fle.de>; > 'apw@...onical.com' <apw@...onical.com>; 'jasowang@...hat.com' > <jasowang@...hat.com>; vkuznets <vkuznets@...hat.com>; > 'marcelo.cerri@...onical.com' <marcelo.cerri@...onical.com> > Subject: [PATCH] Drivers: hv: vmbus: Use raw_smp_processor_id() in > vmbus_connect() > > > With CONFIG_DEBUG_PREEMPT=y, I always see this warning: > BUG: using smp_processor_id() in preemptible [00000000] > > Fix the false warning by using raw_smp_processor_id(). > > Here vmbus_connect() sends a message to the host and waits for the > host's response. The host will deliver the response message and an > interrupt on CPU msg->target_vcpu, and later the interrupt handler > will wake up vmbus_connect(). vmbus_connect() doesn't really have > to run on the same cpu as CPU msg->target_vcpu, so it's safe to > use raw_smp_processor_id() here. > > Signed-off-by: Dexuan Cui <decui@...rosoft.com> > Cc: stable@...r.kernel.org > Cc: K. Y. Srinivasan <kys@...rosoft.com> > Cc: Haiyang Zhang <haiyangz@...rosoft.com> > Cc: Stephen Hemminger <sthemmin@...rosoft.com> > --- > drivers/hv/connection.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c > index ced0418..c3b7040 100644 > --- a/drivers/hv/connection.c > +++ b/drivers/hv/connection.c > @@ -119,8 +119,8 @@ static int vmbus_negotiate_version(struct > vmbus_channel_msginfo *msginfo, > */ > if (version >= VERSION_WIN8_1) { > msg->target_vcpu = > - > hv_cpu_number_to_vp_number(smp_processor_id()); > - vmbus_connection.connect_cpu = smp_processor_id(); > + > hv_cpu_number_to_vp_number(raw_smp_processor_id()); > + vmbus_connection.connect_cpu = raw_smp_processor_id(); Dexuan, We want a consistent view of the CPU we are currently running on. How about doing something like this: diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c index ced041899456..4cc0877ba38a 100644 --- a/drivers/hv/connection.c +++ b/drivers/hv/connection.c @@ -119,8 +119,9 @@ static int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, */ if (version >= VERSION_WIN8_1) { msg->target_vcpu = - hv_cpu_number_to_vp_number(smp_processor_id()); - vmbus_connection.connect_cpu = smp_processor_id(); + hv_cpu_number_to_vp_number(get_cpu()); + vmbus_connection.connect_cpu = msg->target_vcpu; + put_cpu(); } else { msg->target_vcpu = 0; vmbus_connection.connect_cpu = 0; > } else { > msg->target_vcpu = 0; > vmbus_connection.connect_cpu = 0; > -- > 2.7.4
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