linux-kernel - [PATCH] lib/bug: make panic_on_warn available for all architectures

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Message-Id: <1453468336-60133-1-git-send-email-heiko.carstens@de.ibm.com>
Date:	Fri, 22 Jan 2016 14:12:16 +0100
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Christian Borntraeger <borntraeger@...ibm.com>,
	linux-kernel@...r.kernel.org,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Prarit Bhargava <prarit@...hat.com>
Subject: [PATCH] lib/bug: make panic_on_warn available for all architectures

Christian Borntraeger reported that panic_on_warn doesn't have any
effect on s390.

The panic_on_warn feature was introduced with 9e3961a09798 ("kernel:
add panic_on_warn"). However it did care only for the case when
WANT_WARN_ON_SLOWPATH is defined. This is turn is only the case for
architectures which do not have an own __WARN_TAINT defined.

Other architectures which do have __WARN_TAINT defined call
report_bug() for warnings within lib/bug.c which does not call panic()
in case panic_on_warn is set.

Let's simply enable the panic_on_warn feature by adding the same code
like it was added to warn_slowpath_common() in panic.c.

This enables panic_on_warn also for arm64, parisc, powerpc, s390 and
sh.

Cc: Prarit Bhargava <prarit@...hat.com>
Reported-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
---
 lib/bug.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lib/bug.c b/lib/bug.c
index cff145f032a5..6cde380f09de 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -175,6 +175,17 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 			pr_warn("WARNING: at %p [verbose debug info unavailable]\n",
 				(void *)bugaddr);

+		if (panic_on_warn) {
+			/*
+			 * This thread may hit another WARN() in the panic path.
+			 * Resetting this prevents additional WARN() from
+			 * panicking the system on this thread.  Other threads
+			 * are blocked by the panic_mutex in panic().
+			 */
+			panic_on_warn = 0;
+			panic("panic_on_warn set ...\n");
+		}
+
 		print_modules();
 		show_regs(regs);
 		print_oops_end_marker();
-- 
2.3.9