Commit 27e6e7d6 authored May 30, 2019 by Julien Grall Committed by Catalin Marinas Jun 04, 2019

arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs()

cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable
callback. A spin lock is used to ensure the hook is registered before
the rest of the callback is executed.

On -RT spin_lock() may sleep. However, all the callees in stop_machine()
are expected to not sleep. Therefore a raw_spin_lock() is required here.

Given this is already done under stop_machine() and the work done under
the lock is quite small, the latency should not increase too much.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 0c1f14ed

arch/arm64/kernel/cpufeature.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -1194,14 +1194,14 @@ static struct undef_hook ssbs_emulation_hook = {
		static void cpu_enable_ssbs(const struct arm64_cpu_capabilities *__unused)
		{
		static bool undef_hook_registered = false;
		static DEFINE_SPINLOCK(hook_lock);
		static DEFINE_RAW_SPINLOCK(hook_lock);

		spin_lock(&hook_lock);
		raw_spin_lock(&hook_lock);
		if (!undef_hook_registered) {
		register_undef_hook(&ssbs_emulation_hook);
		undef_hook_registered = true;
		}
		spin_unlock(&hook_lock);
		raw_spin_unlock(&hook_lock);

		if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE) {
		sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_DSSBS);

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