Messages in this thread | | | Date | Thu, 18 Oct 2018 17:19:53 +0200 | From | Olaf Hering <> | Subject | Re: [PATCH V2 3/4] vmbus: add per-channel sysfs info |
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Am Sun, 17 Sep 2017 20:54:18 -0700 schrieb kys@exchange.microsoft.com:
> This extends existing vmbus related sysfs structure to provide per-channel > state information. This is useful when diagnosing issues with multiple > queues in networking and storage.
> +++ b/drivers/hv/vmbus_drv.c > +static ssize_t write_avail_show(const struct vmbus_channel *channel, char *buf) > +{ > + const struct hv_ring_buffer_info *rbi = &channel->outbound; > + > + return sprintf(buf, "%u\n", hv_get_bytes_to_write(rbi)); > +} > +VMBUS_CHAN_ATTR_RO(write_avail);
This is upstream since a year.
But I wonder how this can work if vmbus_device_register is called, and then something reads the populated sysfs files before vmbus_open returns. Nothing protects rbi->ring_buffer in this case, which remains NULL until vmbus_open populates it.
A simple reproduce, with a modular kernel, is to boot with init=/bin/bash head /sys/bus/vmbus/devices/*/channels/*/*
Olaf [unhandled content-type:application/pgp-signature] | |