2010/12/14 MichaÅ MirosÅaw <mirqus@xxxxxxxxx>: > 2010/12/14 Mike Waychison <mikew@xxxxxxxxxx>: >> Representing the internal state within netconsole isn't really a boolean >> value, but rather a state machine with transitions. > [...] >> diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c >> index 6e16888..288a025 100644 >> --- a/drivers/net/netconsole.c >> +++ b/drivers/net/netconsole.c > [...] >> @@ -350,9 +362,9 @@ static ssize_t store_enabled(struct netconsole_target *nt, >> Â Â Â Â Â Â Â Âerr = netpoll_setup(&nt->np); >> Â Â Â Â Â Â Â Âspin_lock_irqsave(&target_list_lock, flags); >> Â Â Â Â Â Â Â Âif (err) >> - Â Â Â Â Â Â Â Â Â Â Â nt->enabled = 0; >> + Â Â Â Â Â Â Â Â Â Â Â nt->np_state = NETPOLL_DISABLED; >> Â Â Â Â Â Â Â Âelse >> - Â Â Â Â Â Â Â Â Â Â Â nt->enabled = 1; >> + Â Â Â Â Â Â Â Â Â Â Â nt->np_state = NETPOLL_ENABLED; >> Â Â Â Â Â Â Â Âspin_unlock_irqrestore(&target_list_lock, flags); >> Â Â Â Â Â Â Â Âif (err) >> Â Â Â Â Â Â Â Â Â Â Â Âreturn err; > [...] > > Since the spinlock protects only nt->np_state setting, you might be > able to remove it altogether and use cmpxchg() where nt->np_state > transitions from enabled or disabled state. > > Maybe the locking scheme just needs more thought altogether? The target_list_lock protects the list, as well as the state transitions. This makes iterating through the list and getting a consistent view of the targets a lot easier when it comes time to transmitting packets we are guaranteed that nobody is changing the target state underneath us if nt->np_state == NETPOLL_ENABLED while we hold the lock. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
