Mark Rutland 63a1e1c95e arm64/cpufeature: don't use mutex in bringup path ... Currently, cpus_set_cap() calls static_branch_enable_cpuslocked(), which must take the jump_label mutex. We call cpus_set_cap() in the secondary bringup path, from the idle thread where interrupts are disabled. Taking a mutex in this path "is a NONO" regardless of whether it's contended, and something we must avoid. We didn't spot this until recently, as ___might_sleep() won't warn for this case until all CPUs have been brought up. This patch avoids taking the mutex in the secondary bringup path. The poking of static keys is deferred until enable_cpu_capabilities(), which runs in a suitable context on the boot CPU. To account for the static keys being set later, cpus_have_const_cap() is updated to use another static key to check whether the const cap keys have been initialised, falling back to the caps bitmap until this is the case. This means that users of cpus_have_const_cap() gain should only gain a single additional NOP in the fast path once the const caps are initialised, but should always see the current cap value. The hyp code should never dereference the caps array, since the caps are initialized before we run the module initcall to initialise hyp. A check is added to the hyp init code to document this requirement. This change will sidestep a number of issues when the upcoming hotplug locking rework is merged. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Marc Zyniger <marc.zyngier@arm.com> Reviewed-by: Suzuki Poulose <suzuki.poulose@arm.com> Acked-by: Will Deacon <will.deacon@arm.com> Cc: Christoffer Dall <christoffer.dall@linaro.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Sewior <bigeasy@linutronix.de> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>		2017-05-17 17:00:29 +01:00
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asm	arm64/cpufeature: don't use mutex in bringup path	2017-05-17 17:00:29 +01:00
uapi/asm	Kbuild UAPI header export updates for v4.12	2017-05-10 20:45:36 -07:00