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Date: Tue, 18 Dec 2018 10:53:59 -0800 From: Vineet Gupta <vineet.gupta1@...opsys.com> To: <linux-snps-arc@...ts.infradead.org> CC: <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>, "Vineet Gupta" <vineet.gupta1@...opsys.com> Subject: [PATCH 2/2] ARC: show_regs: fix lockdep splat for good 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@...opsys.com> --- 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
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