On 12/02/18 09:49, Juergen Gross wrote:
On 07/02/18 23:22, Simon Gaiser wrote:
Commit fd8aa9095a95 ("xen: optimize xenbus driver for multiple concurrent xenstore accesses") made a subtle change to the semantic of xenbus_dev_request_and_reply() and xenbus_transaction_end().
Before on an error response to XS_TRANSACTION_END xenbus_dev_request_and_reply() would not decrement the active transaction counter. But xenbus_transaction_end() has always counted the transaction as finished regardless of the response.
Which is correct now. Xenstore will free all transaction related data regardless of the response. A once failed transaction can't be repaired, it has to be repeated completely.
The real problem is decrementing the counter when XS_TRANSACTION_END for a non-existing transaction is being sent.
The new behavior is that xenbus_dev_request_and_reply() and xenbus_transaction_end() will always count the transaction as finished regardless the response code (handled in xs_request_exit()).
ENOENT should not decrement the transaction counter, while all other responses to XS_TRANSACTION_END should still do so.
Sorry, I stand corrected: the ENOENT case should never happen, as this case is tested in xenbus_write_transaction(). It doesn't hurt to test for ENOENT, though.
What should be handled is EINVAL: this would happen if a user specified a string different from "T" and "F".
Juergen