On Wed, Mar 21, 2018 at 2:27 PM, Konstantin Belousov <kostik...@gmail.com> wrote:
> On Thu, Mar 22, 2018 at 04:53:22AM +1100, Bruce Evans wrote: > > Serial console drivers with fast interrupt handlers have much more > > broken locking for ddb special keys. It is invalid to either drop locks > > or call the "any" function from a fast interrupt handler, but buggy > > serial console drivers calls kbd_alt_break(), and that now calls > > shutdown_nice() and other functions that cannot be called from a fast > > interrupt handler. ddb keys supply most of the shutdown_nice() > > functionality for serial consoles, and there are no escape sequence to > > get this without ddb or maybe another debugger, so these bugs don't > > affect most users. > > > > Handling this correctly requires much the same fix as an unsafe signal > > handler, and fixes have much the same problems -- not much more than > > setting a flag is safe, and the flag might never be looked at if the > > system is in a bad state. However, if a nice shutdown is possible then > > the sytem must be in a good enough state to poll for flags. > > Are you saying that fast interrupt handlers call shutdown_nice() ? This > is the quite serious bug on its own. To fix it, shutdown_nice() should > use a fast taskqueue to schedule the task which would lock the process > and send the signal. > Is there some way we know we're in a fast interrupt handler? If so, it should be simple to fix. If not, then there's an API change ahead of us... But bde is right: the system has to be in good enough shape to cope. I wonder if we should put that coping into kdb_reboot() instead. It's only an issue for <CR> TILDE ^R, which is a fairly edge case. Warner _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
