From eac030b22ea12cdfcbb2e941c21c03964403c63f Mon Sep 17 00:00:00 2001 From: Russell Currey Date: Wed, 23 Aug 2023 15:53:17 +1000 Subject: powerpc/pseries: Rework lppaca_shared_proc() to avoid DEBUG_PREEMPT lppaca_shared_proc() takes a pointer to the lppaca which is typically accessed through get_lppaca(). With DEBUG_PREEMPT enabled, this leads to checking if preemption is enabled, for example: BUG: using smp_processor_id() in preemptible [00000000] code: grep/10693 caller is lparcfg_data+0x408/0x19a0 CPU: 4 PID: 10693 Comm: grep Not tainted 6.5.0-rc3 #2 Call Trace: dump_stack_lvl+0x154/0x200 (unreliable) check_preemption_disabled+0x214/0x220 lparcfg_data+0x408/0x19a0 ... This isn't actually a problem however, as it does not matter which lppaca is accessed, the shared proc state will be the same. vcpudispatch_stats_procfs_init() already works around this by disabling preemption, but the lparcfg code does not, erroring any time /proc/powerpc/lparcfg is accessed with DEBUG_PREEMPT enabled. Instead of disabling preemption on the caller side, rework lppaca_shared_proc() to not take a pointer and instead directly access the lppaca, bypassing any potential preemption checks. Fixes: f13c13a00512 ("powerpc: Stop using non-architected shared_proc field in lppaca") Signed-off-by: Russell Currey [mpe: Rework to avoid needing a definition in paca.h and lppaca.h] Signed-off-by: Michael Ellerman Link: https://msgid.link/20230823055317.751786-4-mpe@ellerman.id.au --- drivers/cpuidle/cpuidle-pseries.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) (limited to 'drivers/cpuidle') diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c index a7d33f3ee01e..14db9b7d985d 100644 --- a/drivers/cpuidle/cpuidle-pseries.c +++ b/drivers/cpuidle/cpuidle-pseries.c @@ -414,13 +414,7 @@ static int __init pseries_idle_probe(void) return -ENODEV; if (firmware_has_feature(FW_FEATURE_SPLPAR)) { - /* - * Use local_paca instead of get_lppaca() since - * preemption is not disabled, and it is not required in - * fact, since lppaca_ptr does not need to be the value - * associated to the current CPU, it can be from any CPU. - */ - if (lppaca_shared_proc(local_paca->lppaca_ptr)) { + if (lppaca_shared_proc()) { cpuidle_state_table = shared_states; max_idle_state = ARRAY_SIZE(shared_states); } else { -- cgit v1.2.3