2008/12/13 Gerrit Renker <gerrit@xxxxxxxxxxxxxx>:> | > +static int ccid_request_module(u8 id)> | > +{> | > + if (!in_atomic()) {> | > + ccids_read_lock();> | > + if (ccids[id] == NULL) {> | > + ccids_read_unlock();> | > + return request_module("net-dccp-ccid-%d", id);> | > + }> | > + ccids_read_unlock();> | > + }> | > + return 0;> | > +}> |> | Just a random thought: does this lock really do anything useful here?> |> Reading the (shared) 'ccids' array is the solution chosen to check whether> the module for CCID with number 'id' is already loaded.>> It would be bad to call request_module() each time a new DCCP socket is> opened. Using the 'ccids' array may not be the only way to check whether> a given module (whose name depends on the value of 'id') is loaded.>> But if this solution is chosen, then it requires to protect the read> access to 'ccids', which is shared among all DCCP sockets.
Since the lock is dropped after checking ccids[id] then there'sa window where multiple request_module()s can be called if multipleapplications create a DCCP socket at a same time. The code belowshould do the same without a lock (ccids is a static array,so ccids[N] is always at the same place).
static int ccid_request_module(u8 id){ if (!in_atomic()) { rmb(); if (ccids[id] == NULL) return request_module("net-dccp-ccid-%d", id); } return 0;}
Best Regards,Michał Mirosław˙ôčş{.nÇ+?ˇ?Ž??+%?Ë˙ąéÝśĽ?w˙ş{.nÇ+?ˇ?qĘ˙?{ayş Ę?Ú?ë,j˘fŁ˘ˇh??ď?ę˙?ęçz_čŽ(é???ݢj"?úśm§˙˙žŤţGŤ?é˙˘¸??¨čÚ&Łř§~?á
