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| H A D | entry-armv.S | diff bc089602d206b2abc2d2e8e5324d90342cc0447b Sat Jun 25 12:28:19 CDT 2011 Russell King <rmk+kernel@arm.linux.org.uk> ARM: entry: instrument usr exception handlers with irqsoff tracing
As we no longer re-enable interrupts in these exception handlers, add
the irqsoff tracing calls to them so that the kernel tracks the state
more accurately.
Note that these calls are conditional on IRQSOFF_TRACER:
kernel ----------> user ---------> kernel
^ irqs enabled ^ irqs disabled
No kernel code can run on the local CPU until we've re-entered the
kernel through one of the exception handlers - and userspace can not
take any locks etc. So, the kernel doesn't care about the IRQ mask
state while userspace is running unless we're doing IRQ off latency
tracing. So, we can (and do) avoid the overhead of updating the IRQ
mask state on every kernel->user and user->kernel transition.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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