forked from luck/tmp_suning_uos_patched
044d0d6de9
Problem:
raw_local_irq_save(); // software state on
local_irq_save(); // software state off
...
local_irq_restore(); // software state still off, because we don't enable IRQs
raw_local_irq_restore(); // software state still off, *whoopsie*
existing instances:
- lock_acquire()
raw_local_irq_save()
__lock_acquire()
arch_spin_lock(&graph_lock)
pv_wait() := kvm_wait() (same or worse for Xen/HyperV)
local_irq_save()
- trace_clock_global()
raw_local_irq_save()
arch_spin_lock()
pv_wait() := kvm_wait()
local_irq_save()
- apic_retrigger_irq()
raw_local_irq_save()
apic->send_IPI() := default_send_IPI_single_phys()
local_irq_save()
Possible solutions:
A) make it work by enabling the tracing inside raw_*()
B) make it work by keeping tracing disabled inside raw_*()
C) call it broken and clean it up now
Now, given that the only reason to use the raw_* variant is because you don't
want tracing. Therefore A) seems like a weird option (although it can be done).
C) is tempting, but OTOH it ends up converting a _lot_ of code to raw just
because there is one raw user, this strips the validation/tracing off for all
the other users.
So we pick B) and declare any code that ends up doing:
raw_local_irq_save()
local_irq_save()
lockdep_assert_irqs_disabled();
broken. AFAICT this problem has existed forever, the only reason it came
up is because commit:
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