Patch "powerpc/64: Don't trace irqs-off at interrupt return to soft-disabled context" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

powerpc/64: Don't trace irqs-off at interrupt return to soft-disabled context

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
powerpc-64-don-t-trace-irqs-off-at-interrupt-return-to-soft-disabled-context.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Nicholas Piggin <[email protected]>
Date: Fri, 17 Nov 2017 02:00:50 +1000
Subject: powerpc/64: Don't trace irqs-off at interrupt return to soft-disabled context

From: Nicholas Piggin <[email protected]>

[ Upstream commit acb1feab320e38588fccc568e3767761f494976f ]

When an interrupt is returning to a soft-disabled context (which can happen for non-maskable interrupts or synchronous interrupts), it goes through the motions of soft-disabling again, including calling TRACE_DISABLE_INTS (i.e., trace_hardirqs_off()).

This is not necessary, because we must already be soft-disabled in the interrupt context, it also may be causing crashes in the irq tracing code to re-enter as an nmi. Replace it with a warning to ensure that soft-interrupts are still disabled.

---
 arch/powerpc/kernel/entry_64.S |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

@@ -939,9 +939,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	beq	1f
 	rlwinm	r7,r7,0,~PACA_IRQ_HARD_DIS
 	stb	r7,PACAIRQHAPPENED(r13)
-1:	li	r0,0
-	stb	r0,PACASOFTIRQEN(r13);
-	TRACE_DISABLE_INTS
+1:
+#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_BUG)
+	/* The interrupt should not have soft enabled. */
+	lbz	r7,PACASOFTIRQEN(r13)
+1:	tdnei	r7,0
+	EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
+#endif
 	b	.Ldo_restore
 
 	/*

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/powerpc-64-don-t-trace-irqs-off-at-interrupt-return-to-soft-disabled-context.patch