linux_dsm_epyc7002/include
Steven Rostedt (VMware) 03ecd3f48e rcu/tracing: Add rcu_disabled to denote when rcu_irq_enter() will not work
Tracing uses rcu_irq_enter() as a way to make sure that RCU is watching when
it needs to use rcu_read_lock() and friends. This is because tracing can
happen as RCU is about to enter user space, or about to go idle, and RCU
does not watch for RCU read side critical sections as it makes the
transition.

There is a small location within the RCU infrastructure that rcu_irq_enter()
itself will not work. If tracing were to occur in that section it will break
if it tries to use rcu_irq_enter().

Originally, this happens with the stack_tracer, because it will call
save_stack_trace when it encounters stack usage that is greater than any
stack usage it had encountered previously. There was a case where that
happened in the RCU section where rcu_irq_enter() did not work, and lockdep
complained loudly about it. To fix it, stack tracing added a call to be
disabled and RCU would disable stack tracing during the critical section
that rcu_irq_enter() was inoperable. This solution worked, but there are
other cases that use rcu_irq_enter() and it would be a good idea to let RCU
give a way to let others know that rcu_irq_enter() will not work. For
example, in trace events.

Another helpful aspect of this change is that it also moves the per cpu
variable called in the RCU critical section into a cache locale along with
other RCU per cpu variables used in that same location.

I'm keeping the stack_trace_disable() code, as that still could be used in
the future by places that really need to disable it. And since it's only a
static inline, it wont take up any kernel text if it is not used.

Link: http://lkml.kernel.org/r/20170405093207.404f8deb@gandalf.local.home

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2017-04-10 15:22:03 -04:00
..
acpi Merge branches 'acpi-bus', 'acpi-sleep' and 'acpi-processor' 2017-02-20 14:28:03 +01:00
asm-generic mm: convert generic code to 5-level paging 2017-03-09 11:48:47 -08:00
clocksource
crypto net: Work around lockdep limitation in sockets that use sockets 2017-03-09 18:23:27 -08:00
drm sched/headers: Prepare to remove the <linux/mm_types.h> dependency from <linux/sched.h> 2017-03-02 08:42:37 +01:00
dt-bindings scripts/spelling.txt: add "overide" pattern and fix typo instances 2017-03-09 17:01:09 -08:00
keys KEYS: Differentiate uses of rcu_dereference_key() and user_key_payload() 2017-03-02 10:09:00 +11:00
kvm
linux rcu/tracing: Add rcu_disabled to denote when rcu_irq_enter() will not work 2017-04-10 15:22:03 -04:00
math-emu
media media fixes for v4.11-rc2 2017-03-09 15:50:56 -08:00
memory
misc
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-03-14 21:31:23 -07:00
pcmcia
ras
rdma sched/headers: Prepare to remove <linux/cred.h> inclusion from <linux/sched.h> 2017-03-02 08:42:31 +01:00
rxrpc
scsi scsi: mpt3sas: Avoid sleeping in interrupt context 2017-03-01 21:52:13 -05:00
soc ARC updates for 4.11 rc1 2017-02-22 10:33:53 -08:00
sound sched/headers: Prepare to remove spurious <linux/sched.h> inclusion dependencies 2017-03-02 08:42:41 +01:00
target target: fix ALUA transition timeout handling 2017-03-18 14:47:28 -07:00
trace There was some breakage with the changes for jump labels in the 4.11 merge 2017-03-07 09:37:28 -08:00
uapi amd, intel, tilcdc, omap, and malidp fixes. 2017-03-17 11:19:52 -07:00
video
xen Merge branch 'stable/for-linus-4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb 2017-03-07 10:23:17 -08:00
Kbuild