4.4-stable patches

added patches:
	serial-sh-sci-remove-cpufreq-notifier-to-fix-crash-deadlock.patch

diff --git a/queue-4.4/serial-sh-sci-remove-cpufreq-notifier-to-fix-crash-deadlock.patch b/queue-4.4/serial-sh-sci-remove-cpufreq-notifier-to-fix-crash-deadlock.patch
new file mode 100644 (file)
index 0000000..faef98c
--- /dev/null
+++ b/queue-4.4/serial-sh-sci-remove-cpufreq-notifier-to-fix-crash-deadlock.patch
@@ -0,0 +1,123 @@
+From ff1cab374ad98f4b9f408525ca9c08992b4ed784 Mon Sep 17 00:00:00 2001
+From: Geert Uytterhoeven <geert+renesas@glider.be>
+Date: Tue, 5 Jan 2016 19:36:37 +0100
+Subject: serial: sh-sci: Remove cpufreq notifier to fix crash/deadlock
+
+From: Geert Uytterhoeven <geert+renesas@glider.be>
+
+commit ff1cab374ad98f4b9f408525ca9c08992b4ed784 upstream.
+
+The BSP team noticed that there is spin/mutex lock issue on sh-sci when
+CPUFREQ is used.  The issue is that the notifier function may call
+mutex_lock() while the spinlock is held, which can lead to a BUG().
+This may happen if CPUFREQ is changed while another CPU calls
+clk_get_rate().
+
+Taking the spinlock was added to the notifier function in commit
+e552de2413edad1a ("sh-sci: add platform device private data"), to
+protect the list of serial ports against modification during traversal.
+At that time the Common Clock Framework didn't exist yet, and
+clk_get_rate() just returned clk->rate without taking a mutex.
+Note that since commit d535a2305facf9b4 ("serial: sh-sci: Require a
+device per port mapping."), there's no longer a list of serial ports to
+traverse, and taking the spinlock became superfluous.
+
+To fix the issue, just remove the cpufreq notifier:
+  1. The notifier doesn't work correctly: all it does is update stored
+     clock rates; it does not update the divider in the hardware.
+     The divider will only be updated when calling sci_set_termios().
+     I believe this was broken back in 2004, when the old
+     drivers/char/sh-sci.c driver (where the notifier did update the
+     divider) was replaced by drivers/serial/sh-sci.c (where the
+     notifier just updated port->uartclk).
+     Cfr. full-history-linux commits 6f8deaef2e9675d9 ("[PATCH] sh: port
+     sh-sci driver to the new API") and 3f73fe878dc9210a ("[PATCH]
+     Remove old sh-sci driver").
+  2. On modern SoCs, the sh-sci parent clock rate is no longer related
+     to the CPU clock rate anyway, so using a cpufreq notifier is
+     futile.
+
+Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+
+---
+ drivers/tty/serial/sh-sci.c |   39 ---------------------------------------
+ 1 file changed, 39 deletions(-)
+
+--- a/drivers/tty/serial/sh-sci.c
++++ b/drivers/tty/serial/sh-sci.c
+@@ -38,7 +38,6 @@
+ #include <linux/major.h>
+ #include <linux/module.h>
+ #include <linux/mm.h>
+-#include <linux/notifier.h>
+ #include <linux/of.h>
+ #include <linux/platform_device.h>
+ #include <linux/pm_runtime.h>
+@@ -116,8 +115,6 @@ struct sci_port {
+       struct timer_list               rx_timer;
+       unsigned int                    rx_timeout;
+ #endif
+-
+-      struct notifier_block           freq_transition;
+ };
+ 
+ #define SCI_NPORTS CONFIG_SERIAL_SH_SCI_NR_UARTS
+@@ -1606,29 +1603,6 @@ static irqreturn_t sci_mpxed_interrupt(i
+       return ret;
+ }
+ 
+-/*
+- * Here we define a transition notifier so that we can update all of our
+- * ports' baud rate when the peripheral clock changes.
+- */
+-static int sci_notifier(struct notifier_block *self,
+-                      unsigned long phase, void *p)
+-{
+-      struct sci_port *sci_port;
+-      unsigned long flags;
+-
+-      sci_port = container_of(self, struct sci_port, freq_transition);
+-
+-      if (phase == CPUFREQ_POSTCHANGE) {
+-              struct uart_port *port = &sci_port->port;
+-
+-              spin_lock_irqsave(&port->lock, flags);
+-              port->uartclk = clk_get_rate(sci_port->iclk);
+-              spin_unlock_irqrestore(&port->lock, flags);
+-      }
+-
+-      return NOTIFY_OK;
+-}
+-
+ static const struct sci_irq_desc {
+       const char      *desc;
+       irq_handler_t   handler;
+@@ -2559,9 +2533,6 @@ static int sci_remove(struct platform_de
+ {
+       struct sci_port *port = platform_get_drvdata(dev);
+ 
+-      cpufreq_unregister_notifier(&port->freq_transition,
+-                                  CPUFREQ_TRANSITION_NOTIFIER);
+-
+       uart_remove_one_port(&sci_uart_driver, &port->port);
+ 
+       sci_cleanup_single(port);
+@@ -2714,16 +2685,6 @@ static int sci_probe(struct platform_dev
+       if (ret)
+               return ret;
+ 
+-      sp->freq_transition.notifier_call = sci_notifier;
+-
+-      ret = cpufreq_register_notifier(&sp->freq_transition,
+-                                      CPUFREQ_TRANSITION_NOTIFIER);
+-      if (unlikely(ret < 0)) {
+-              uart_remove_one_port(&sci_uart_driver, &sp->port);
+-              sci_cleanup_single(sp);
+-              return ret;
+-      }
+-
+ #ifdef CONFIG_SH_STANDARD_BIOS
+       sh_bios_gdb_detach();
+ #endif

diff --git a/queue-4.4/series b/queue-4.4/series
index f3e62555ef52c33e83973c86c4daa58ed0bc9640..14cb561b5f2ee4f3b0b2a1d5c8e1337fac2fecb5 100644 (file)
--- a/queue-4.4/series
+++ b/queue-4.4/series
@@ -136,3 +136,4 @@ perf-evlist-reference-count-the-cpu-and-thread-maps-at-set_maps.patch
 spi-rockchip-modify-dma-max-burst-to-1.patch
 x86-mm-kmmio-fix-mmiotrace-for-hugepages.patch
 ext4-fix-null-pointer-dereference-in-ext4_mark_inode_dirty.patch
+serial-sh-sci-remove-cpufreq-notifier-to-fix-crash-deadlock.patch