From: Vineet Gupta <vineet.gupta1@synopsys.com>
To: <linux-snps-arc@lists.infradead.org>
Cc: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
<linux-arch@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Vineet Gupta" <vineet.gupta1@synopsys.com>
Subject: [PATCH 2/2] ARC: show_regs: fix lockdep splat for good
Date: Tue, 18 Dec 2018 10:53:59 -0800 [thread overview]
Message-ID: <1545159239-30628-3-git-send-email-vgupta@synopsys.com> (raw)
In-Reply-To: <1545159239-30628-1-git-send-email-vgupta@synopsys.com>
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@synopsys.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
next prev parent reply other threads:[~2018-12-18 18:54 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-18 18:53 [PATCH 0/2] ARC show_regs fixes Vineet Gupta
2018-12-18 18:53 ` [PATCH 1/2] ARC: show_regs: avoid page allocator Vineet Gupta
2018-12-19 17:04 ` Eugeniy Paltsev
2018-12-19 17:36 ` Vineet Gupta
2018-12-20 1:16 ` Vineet Gupta
2018-12-20 13:30 ` Tetsuo Handa
2018-12-20 18:36 ` Vineet Gupta
2018-12-20 18:43 ` Vineet Gupta
2018-12-19 20:46 ` William Kucharski
2018-12-19 21:36 ` Vineet Gupta
2018-12-20 12:57 ` Michal Hocko
2018-12-20 18:38 ` Vineet Gupta
2018-12-18 18:53 ` Vineet Gupta [this message]
2018-12-20 13:04 ` [PATCH 2/2] ARC: show_regs: fix lockdep splat for good Michal Hocko
2018-12-20 18:45 ` Vineet Gupta
2018-12-21 13:04 ` Michal Hocko
2018-12-21 13:27 ` Michal Hocko
2018-12-21 17:55 ` Vineet Gupta
2018-12-24 19:10 ` Michal Hocko
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