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authorOlaf Hering <olaf@aepfle.de>2015-12-15 01:01:33 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-12-15 04:12:21 +0100
commit3cace4a616108539e2730f8dc21a636474395e0f (patch)
tree431580a2995465901957035bfd024e038ba8ebf3 /drivers/hv/hv_kvp.c
parentDrivers: hv: util: Increase the timeout for util services (diff)
downloadlinux-3cace4a616108539e2730f8dc21a636474395e0f.tar.xz
linux-3cace4a616108539e2730f8dc21a636474395e0f.zip
Drivers: hv: utils: run polling callback always in interrupt context
All channel interrupts are bound to specific VCPUs in the guest at the point channel is created. While currently, we invoke the polling function on the correct CPU (the CPU to which the channel is bound to) in some cases we may run the polling function in a non-interrupt context. This potentially can cause an issue as the polling function can be interrupted by the channel callback function. Fix the issue by running the polling function on the appropriate CPU at interrupt level. Additional details of the issue being addressed by this patch are given below: Currently hv_fcopy_onchannelcallback is called from interrupts and also via the ->write function of hv_utils. Since the used global variables to maintain state are not thread safe the state can get out of sync. This affects the variable state as well as the channel inbound buffer. As suggested by KY adjust hv_poll_channel to always run the given callback on the cpu which the channel is bound to. This avoids the need for locking because all the util services are single threaded and only one transaction is active at any given point in time. Additionally, remove the context variable, they will always be the same as recv_channel. Signed-off-by: Olaf Hering <olaf@aepfle.de> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/hv/hv_kvp.c')
-rw-r--r--drivers/hv/hv_kvp.c28
1 files changed, 10 insertions, 18 deletions
diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index e6aa33a89b0e..2a3420c4ca59 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -66,7 +66,6 @@ static struct {
struct hv_kvp_msg *kvp_msg; /* current message */
struct vmbus_channel *recv_channel; /* chn we got the request */
u64 recv_req_id; /* request ID. */
- void *kvp_context; /* for the channel callback */
} kvp_transaction;
/*
@@ -94,6 +93,13 @@ static struct hvutil_transport *hvt;
*/
#define HV_DRV_VERSION "3.1"
+static void kvp_poll_wrapper(void *channel)
+{
+ /* Transaction is finished, reset the state here to avoid races. */
+ kvp_transaction.state = HVUTIL_READY;
+ hv_kvp_onchannelcallback(channel);
+}
+
static void
kvp_register(int reg_value)
{
@@ -121,12 +127,7 @@ static void kvp_timeout_func(struct work_struct *dummy)
*/
kvp_respond_to_host(NULL, HV_E_FAIL);
- /* Transaction is finished, reset the state. */
- if (kvp_transaction.state > HVUTIL_READY)
- kvp_transaction.state = HVUTIL_READY;
-
- hv_poll_channel(kvp_transaction.kvp_context,
- hv_kvp_onchannelcallback);
+ hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
}
static int kvp_handle_handshake(struct hv_kvp_msg *msg)
@@ -218,9 +219,7 @@ static int kvp_on_msg(void *msg, int len)
*/
if (cancel_delayed_work_sync(&kvp_timeout_work)) {
kvp_respond_to_host(message, error);
- kvp_transaction.state = HVUTIL_READY;
- hv_poll_channel(kvp_transaction.kvp_context,
- hv_kvp_onchannelcallback);
+ hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
}
return 0;
@@ -596,15 +595,8 @@ void hv_kvp_onchannelcallback(void *context)
int util_fw_version;
int kvp_srv_version;
- if (kvp_transaction.state > HVUTIL_READY) {
- /*
- * We will defer processing this callback once
- * the current transaction is complete.
- */
- kvp_transaction.kvp_context = context;
+ if (kvp_transaction.state > HVUTIL_READY)
return;
- }
- kvp_transaction.kvp_context = NULL;
vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 4, &recvlen,
&requestid);