From: Heiko Carstens Date: Wed, 10 Feb 2016 13:13:24 +0000 (+0100) Subject: s390/diag: avoid lockdep recursion X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=f6c9b160233f9b5afe926b91b55589b706076640;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git s390/diag: avoid lockdep recursion The diagnose tracer will indirectly call back into the lockdep code when lockdep does not expect it (arch_spinlock). This causes lockdep to disable itself and therefore we don't have a working lock dependency validator anymore. This patch effectively disables tracing of diag 0x9c and 0x44 if lockdep is enabled. If however lockdep is enabled spinlocks are mainly implemented using a trylock variant, which will not issue any diag 0x9c or 0x44. So this change has hardly any effect on tracing except when arch_spinlock and friends are explicitly used. Reported-and-Tested-by: David Hildenbrand Signed-off-by: Heiko Carstens Reviewed-by: David Hildenbrand Acked-by: Martin Schwidefsky Signed-off-by: Martin Schwidefsky --- diff --git a/arch/s390/kernel/trace.c b/arch/s390/kernel/trace.c index 21a5df99552b..dde7654f5c68 100644 --- a/arch/s390/kernel/trace.c +++ b/arch/s390/kernel/trace.c @@ -18,6 +18,9 @@ void trace_s390_diagnose_norecursion(int diag_nr) unsigned long flags; unsigned int *depth; + /* Avoid lockdep recursion. */ + if (IS_ENABLED(CONFIG_LOCKDEP)) + return; local_irq_save(flags); depth = this_cpu_ptr(&diagnose_trace_depth); if (*depth == 0) {