> On 28 Apr 2023, at 14:03, Alexander Bluhm <alexander.bl...@gmx.net> wrote:
>
> That basically means we must never call one of the pool get or put
> functions with kernel lock. This may be the case currently. But
> at this stage while we are pushing locks around the network code,
> I would like to keep it as it is.
>
> Allowing net interrupts during route pool get mutex gains nearly
> nothing. It makes placing a kernel lock in our transition process
> harder.
>
> bluhm
This is not true. The IPL is not kerne lock or MP related. Each pool(9)
uses its own mutex(9) or rwlock(9) for protection. This depends on
PR_RWLOCK flag passed to pool_init(9). The spl*(9) only disables
interrupts with level less or equal priority on this CPU. Non system
wide. On the uniprocessor machine you can’t spin in mutex(9) because it
is the deadlock, so you only disable interrupts within mutex(9) protected
critical section. But SMP machine is the different case. In the ancient
MP times interrupts were enabled on boot cpu only, so spl*(9) really
provided protection, but since interrupts were enabled on application
CPUs too this stopped to work, because the interrupts you disabled on
this cpu could happen on any other. IPL_MPFLOOR has very high level and
I guess it was chosen mostly for insurance.
We do rt allocation and release in the sockets, ioctl and softnet
context, so I see no reason to disable interrupts with priority greater
than IPL_SOFTNET.
>
> On Thu, Apr 27, 2023 at 02:18:11AM +0300, Vitaliy Makkoveev wrote:
>> Index: sys/net/route.c
>> ===================================================================
>> RCS file: /cvs/src/sys/net/route.c,v
>> retrieving revision 1.418
>> diff -u -p -r1.418 route.c
>> --- sys/net/route.c 26 Apr 2023 16:09:44 -0000 1.418
>> +++ sys/net/route.c 26 Apr 2023 23:00:02 -0000
>> @@ -176,7 +176,7 @@ route_init(void)
>> {
>> rtcounters = counters_alloc(rts_ncounters);
>>
>> - pool_init(&rtentry_pool, sizeof(struct rtentry), 0, IPL_MPFLOOR, 0,
>> + pool_init(&rtentry_pool, sizeof(struct rtentry), 0, IPL_SOFTNET, 0,
>> "rtentry", NULL);
>>
>> while (rt_hashjitter == 0)
>
