From 24326039b9685e8bfb1532932e18cb458f2a3517 Mon Sep 17 00:00:00 2001 From: "K. Y. Srinivasan" Date: Wed, 31 Aug 2011 14:35:57 -0700 Subject: [PATCH] Staging: hv: vmbus: Cleanup the code in process_chn_event() A channel in Hyper-V is equivalent to a device. Thus, a channel is persistent once it is presented to the guest, even if the driver managing this device is unloaded. By checking and invoking the driver specific callback function under the protection of the channel inbound_lock, we can properly deal with racing driver unloads since an unloading driver sets the callback to NULL under the protection of this inbound_lock. Signed-off-by: K. Y. Srinivasan Signed-off-by: Haiyang Zhang Signed-off-by: Greg Kroah-Hartman --- drivers/staging/hv/connection.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/staging/hv/connection.c b/drivers/staging/hv/connection.c index 9e99c044b23f..649b91bcd8c1 100644 --- a/drivers/staging/hv/connection.c +++ b/drivers/staging/hv/connection.c @@ -219,11 +219,25 @@ static void process_chn_event(u32 relid) */ channel = relid2channel(relid); + if (!channel) { + pr_err("channel not found for relid - %u\n", relid); + return; + } + + /* + * A channel once created is persistent even when there + * is no driver handling the device. An unloading driver + * sets the onchannel_callback to NULL under the + * protection of the channel inbound_lock. Thus, checking + * and invoking the driver specific callback takes care of + * orderly unloading of the driver. + */ + spin_lock_irqsave(&channel->inbound_lock, flags); - if (channel && (channel->onchannel_callback != NULL)) + if (channel->onchannel_callback != NULL) channel->onchannel_callback(channel->channel_callback_context); else - pr_err("channel not found for relid - %u\n", relid); + pr_err("no channel callback for relid - %u\n", relid); spin_unlock_irqrestore(&channel->inbound_lock, flags); }