On Fri, 2020-01-24 at 19:38 +0200, Andy Shevchenko wrote: > On Fri, Jan 24, 2020 at 08:39:02AM -0800, James Bottomley wrote: > > On Fri, 2020-01-24 at 18:07 +0200, Andy Shevchenko wrote: > > > Replace open coded single-linked list iteration loop with > > > for_each_console() > > > helper in use. > > > - while ((console = console_drivers) != NULL) > > > - unregister_console(console_drivers); > > > + for_each_console(console) > > > + unregister_console(console); > > > > This is wrong. The old formulation iterates correctly in the face > > of element removal. for_each_console is defined: > > > > #define for_each_console(con) \ > > for (con = console_drivers; con != NULL; con = con->next) > > > > So it's not safe for any iteration that alters the list elements. > > Ah, I see. In this case we need to keep a pointer to the next > element. Though, the original code assumes that console_drivers after > unregistration will be promoted to the next element. Do we have this > assumption solid? Yes, the original code simply removes the head until the list is empty. That's a recognized way of emptying any list while letting the remove code take care of the locking ... it works because parisc doesn't have a braille console. James
