On Wed, Mar 22, 2017 at 10:54:15AM +0100, Julia Lawall wrote:
> On Tue, 21 Mar 2017, Julia Cartwright wrote:
> > On PREEMPT_RT, the spinlock_t type becomes an object which sleeps under
> > contention. The codepaths used to support scheduling (irq dispatching, arch
> > code, the scheduler, timers) therefore must make use of the
> > raw_spin_lock{,_irq,_irqsave}() variations which preserve the non-sleeping
> > spinlock behavior.
> >
> > Because the irq_chip callbacks are invoked in the process of interrupt
> > dispatch, they cannot therefore make use of spin_lock_t type. Instead, the
> > usage of raw_spinlock_t is appropriate.
> >
> > Provide a spatch to identify (and attempt to patch) such problematic irqchip
> > implementations.
> >
> > Note to those generating patches using this spatch; in order to maintain
> > correct semantics w/ PREEMPT_RT, it is necessary to audit the
> > raw_spinlock_t-protected codepaths to ensure their execution is bounded and
> > minimal. This is a manual audit process.
> >
> > See commit 47b03ca903fb0 ("pinctrl: qcom: Use raw spinlock variants") as an
> > example of _one_ such instance, which fixed a real bug seen in the field.
> >
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> > Signed-off-by: Julia Cartwright <julia@xxxxxx>
>
> Acked-by: Julia Lawall <julia.lawall@xxxxxxx>
Thanks, Julia.
How do these semantic patches normally land? It looks like they quite a
few have gone through the kbuild tree, is this the norm?
Thanks,
Other Julia
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