signal handling core calls ARCH show_regs() with preemption disabled
which causes __might_sleep functions such as mmput leading to lockdep
splat. Workaround by re-enabling preemption temporarily.
This may not be as bad as it sounds since the preemption disabling
itself was introduced for a supressing smp_processor_id() warning in x86
code by commit 3a9f84d354ce ("signals, debug: fix BUG: using
smp_processor_id() in preemptible code in print_fatal_signal()")
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
---
arch/arc/kernel/troubleshoot.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c
index 2885bec71fb8..c650d3de13e1 100644
--- a/arch/arc/kernel/troubleshoot.c
+++ b/arch/arc/kernel/troubleshoot.c
@@ -177,6 +177,12 @@ void show_regs(struct pt_regs *regs)
struct task_struct *tsk = current;
struct callee_regs *cregs;
+ /*
+ * generic code calls us with preemption disabled, but some calls
+ * here could sleep, so re-enable to avoid lockdep splat
+ */
+ preempt_enable();
+
print_task_path_n_nm(tsk);
show_regs_print_info(KERN_INFO);
@@ -219,6 +225,8 @@ void show_regs(struct pt_regs *regs)
cregs = (struct callee_regs *)current->thread.callee_reg;
if (cregs)
show_callee_regs(cregs);
+
+ preempt_disable();
}
void show_kernel_fault_diag(const char *str, struct pt_regs *regs,
--
2.7.4
