| Message ID | 1429854752-5698-1-git-send-email-mpe@ellerman.id.au (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Michael Ellerman |
| Headers | show |
From: Michael Ellerman <mpe@ellerman.id.au> Date: Fri, 24 Apr 2015 15:52:32 +1000 > The recent commit to only register the EHEA memory hotplug hooks on > adapter probe has a few problems. > > Firstly the reference counting is wrong for multiple adapters, in that > the hooks are registered multiple times. Secondly the check in the tear > down path is backward. Finally the error path doesn't decrement the > count. > > The multiple registration of the hooks is the biggest problem, as it > leads to oopses when the system is rebooted, and/or errors during memory > hotplug, eg: ... > Fixes: aa183323312d ("ehea: Register memory hotplug, reboot and crash hooks on adapter probe") > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Applied, but using an atomic counter for this is really inappropriate and is what lead to this bug in the first place. You're not counting anything, because if you were, then you would be decrementing this thing somewhere. Rather, it's purely a boolean state saying "I did X". So it should be a boolean, and no atomicity nor other special considerations are needed for setting it to true.
On Sat, 2015-04-25 at 14:43 -0400, David Miller wrote: > From: Michael Ellerman <mpe@ellerman.id.au> > Date: Fri, 24 Apr 2015 15:52:32 +1000 > > > The recent commit to only register the EHEA memory hotplug hooks on > > adapter probe has a few problems. > > > > Firstly the reference counting is wrong for multiple adapters, in that > > the hooks are registered multiple times. Secondly the check in the tear > > down path is backward. Finally the error path doesn't decrement the > > count. > > > > The multiple registration of the hooks is the biggest problem, as it > > leads to oopses when the system is rebooted, and/or errors during memory > > hotplug, eg: > ... > > Fixes: aa183323312d ("ehea: Register memory hotplug, reboot and crash hooks on adapter probe") > > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> > > Applied, but using an atomic counter for this is really inappropriate > and is what lead to this bug in the first place. > > You're not counting anything, because if you were, then you would be > decrementing this thing somewhere. > > Rather, it's purely a boolean state saying "I did X". So it should be > a boolean, and no atomicity nor other special considerations are > needed for setting it to true. Yeah I agree, it's a mess. We should be unregistering the hooks when the last adapter is removed, which is where we'd do the decrement. As it's written the hooks stay registered until the driver is removed. I'll try and find time, or someone else with time, to fix it up properly for 4.2. cheers
diff --git a/drivers/net/ethernet/ibm/ehea/ehea_main.c b/drivers/net/ethernet/ibm/ehea/ehea_main.c index c05e50759621..00d86be0c831 100644 --- a/drivers/net/ethernet/ibm/ehea/ehea_main.c +++ b/drivers/net/ethernet/ibm/ehea/ehea_main.c @@ -3347,7 +3347,7 @@ static int ehea_register_memory_hooks(void) { int ret = 0; - if (atomic_inc_and_test(&ehea_memory_hooks_registered)) + if (atomic_inc_return(&ehea_memory_hooks_registered) > 1) return 0; ret = ehea_create_busmap(); @@ -3381,12 +3381,14 @@ out3: out2: unregister_reboot_notifier(&ehea_reboot_nb); out: + atomic_dec(&ehea_memory_hooks_registered); return ret; } static void ehea_unregister_memory_hooks(void) { - if (atomic_read(&ehea_memory_hooks_registered)) + /* Only remove the hooks if we've registered them */ + if (atomic_read(&ehea_memory_hooks_registered) == 0) return; unregister_reboot_notifier(&ehea_reboot_nb);
The recent commit to only register the EHEA memory hotplug hooks on adapter probe has a few problems. Firstly the reference counting is wrong for multiple adapters, in that the hooks are registered multiple times. Secondly the check in the tear down path is backward. Finally the error path doesn't decrement the count. The multiple registration of the hooks is the biggest problem, as it leads to oopses when the system is rebooted, and/or errors during memory hotplug, eg: $ ./mem-on-off-test.sh -r 2 ... ehea: memory is going offline ehea: LPAR memory changed - re-initializing driver ehea: re-initializing driver complete ehea: memory is going offline ehea: LPAR memory changed - re-initializing driver ehea: opcode=26c ret=fffffffffffffffc arg1=8000000003000003 arg2=0 arg3=700000060000d600 arg4=3fded0000 arg5=200 arg6=0 arg7=0 ehea: register_rpage_mr failed ehea: registering mr failed ehea: register MR failed - driver inoperable! ehea: memory is going offline Fixes: aa183323312d ("ehea: Register memory hotplug, reboot and crash hooks on adapter probe") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> --- drivers/net/ethernet/ibm/ehea/ehea_main.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)