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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>
This commit is contained in:
Julien Grall 2019-05-30 12:30:58 +01:00 committed by Catalin Marinas
parent 0c1f14ed12
commit 27e6e7d63f
1 changed files with 3 additions and 3 deletions
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6
arch/arm64/kernel/cpufeature.c
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@ -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);