6.18-stable review patch. If anyone has any objections, please let me know.
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From: Sebastian Andrzej Siewior bigeasy@linutronix.de
[ Upstream commit c94291914b200e10c72cef23c8e4c67eb4fdbcd9 ]
On SMP systems the CPU hotplug callbacks in the "starting" range are invoked while the CPU is brought up and interrupts are still disabled. Callbacks which are added later are invoked via the hotplug-thread on the target CPU and interrupts are explicitly disabled.
In the UP case callbacks which are added later are invoked directly without the thread indirection. This is in principle okay since there is just one CPU but those callbacks are invoked with interrupt disabled code. That's incorrect as those callbacks assume interrupt disabled context.
Disable interrupts before invoking the callbacks on UP if the state is atomic and interrupts are expected to be disabled. The "save" part is required because this is also invoked early in the boot process while interrupts are disabled and must not be enabled prematurely.
Fixes: 06ddd17521bf1 ("sched/smp: Always define is_percpu_thread() and scheduler_ipi()") Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Link: https://patch.msgid.link/20251127144723.ev9DuXXR@linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/cpu.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c index db9f6c539b28c..15000c7abc659 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -249,6 +249,14 @@ static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state, return ret; }
+/* + * The former STARTING/DYING states, ran with IRQs disabled and must not fail. + */ +static bool cpuhp_is_atomic_state(enum cpuhp_state state) +{ + return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE; +} + #ifdef CONFIG_SMP static bool cpuhp_is_ap_state(enum cpuhp_state state) { @@ -271,14 +279,6 @@ static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup) complete(done); }
-/* - * The former STARTING/DYING states, ran with IRQs disabled and must not fail. - */ -static bool cpuhp_is_atomic_state(enum cpuhp_state state) -{ - return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE; -} - /* Synchronization state management */ enum cpuhp_sync_state { SYNC_STATE_DEAD, @@ -2364,7 +2364,14 @@ static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup, else ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL); #else - ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL); + if (cpuhp_is_atomic_state(state)) { + guard(irqsave)(); + ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL); + /* STARTING/DYING must not fail! */ + WARN_ON_ONCE(ret); + } else { + ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL); + } #endif BUG_ON(ret && !bringup); return ret;