linux-kernel - [PATCH 4.9 18/87] powerpc/powernv: Fix NVRAM sleep in invalid context when crashing

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Message-Id: <20180521210421.964411464@linuxfoundation.org>
Date:   Mon, 21 May 2018 23:10:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nicholas Piggin <npiggin@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.9 18/87] powerpc/powernv: Fix NVRAM sleep in invalid context when crashing

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Piggin <npiggin@...il.com>

commit c1d2a31397ec51f0370f6bd17b19b39152c263cb upstream.

Similarly to opal_event_shutdown, opal_nvram_write can be called in
the crash path with irqs disabled. Special case the delay to avoid
sleeping in invalid context.

Fixes: 3b8070335f75 ("powerpc/powernv: Fix OPAL NVRAM driver OPAL_BUSY loops")
Cc: stable@...r.kernel.org # v3.2
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/platforms/powernv/opal-nvram.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/arch/powerpc/platforms/powernv/opal-nvram.c
+++ b/arch/powerpc/platforms/powernv/opal-nvram.c
@@ -44,6 +44,10 @@ static ssize_t opal_nvram_read(char *buf
 	return count;
 }
 
+/*
+ * This can be called in the panic path with interrupts off, so use
+ * mdelay in that case.
+ */
 static ssize_t opal_nvram_write(char *buf, size_t count, loff_t *index)
 {
 	s64 rc = OPAL_BUSY;
@@ -58,10 +62,16 @@ static ssize_t opal_nvram_write(char *bu
 	while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
 		rc = opal_write_nvram(__pa(buf), count, off);
 		if (rc == OPAL_BUSY_EVENT) {
-			msleep(OPAL_BUSY_DELAY_MS);
+			if (in_interrupt() || irqs_disabled())
+				mdelay(OPAL_BUSY_DELAY_MS);
+			else
+				msleep(OPAL_BUSY_DELAY_MS);
 			opal_poll_events(NULL);
 		} else if (rc == OPAL_BUSY) {
-			msleep(OPAL_BUSY_DELAY_MS);
+			if (in_interrupt() || irqs_disabled())
+				mdelay(OPAL_BUSY_DELAY_MS);
+			else
+				msleep(OPAL_BUSY_DELAY_MS);
 		}
 	}