[rt] Update to 5.0.10-rt7 and re-enable

1 files changed, 85 insertions, 0 deletions

diff --git a/debian/patches-rt/printk-kmsg_dump-remove-mutex-usage.patch b/debian/patches-rt/printk-kmsg_dump-remove-mutex-usage.patch
new file mode 100644
index 000000000..e3d259e7a
--- /dev/null
+++ b/debian/patches-rt/printk-kmsg_dump-remove-mutex-usage.patch
@@ -0,0 +1,85 @@
+From: John Ogness <john.ogness@linutronix.de>
+Date: Wed, 24 Apr 2019 16:36:04 +0200
+Subject: [PATCH] printk: kmsg_dump: remove mutex usage
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.0/older/patches-5.0.10-rt7.tar.xz
+
+The kmsg dumper can be called from any context, but the dumping
+helpers were using a mutex to synchronize the iterator against
+concurrent dumps.
+
+Rather than trying to synchronize the iterator, use a local copy
+of the iterator during the dump. Then no synchronization is
+required.
+
+Reported-by: Scott Wood <swood@redhat.com>
+Signed-off-by: John Ogness <john.ogness@linutronix.de>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/printk/printk.c |   23 ++++++++++-------------
+ 1 file changed, 10 insertions(+), 13 deletions(-)
+
+--- a/kernel/printk/printk.c
++++ b/kernel/printk/printk.c
+@@ -359,8 +359,6 @@ static u64 syslog_seq;
+ static size_t syslog_partial;
+ static bool syslog_time;
+ 
+-static DEFINE_MUTEX(kmsg_dump_lock);
+-
+ /* the last printk record at the last 'clear' command */
+ static u64 clear_seq;
+ 
+@@ -2820,6 +2818,7 @@ module_param_named(always_kmsg_dump, alw
+  */
+ void kmsg_dump(enum kmsg_dump_reason reason)
+ {
++	struct kmsg_dumper dumper_local;
+ 	struct kmsg_dumper *dumper;
+ 
+ 	if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
+@@ -2830,16 +2829,18 @@ void kmsg_dump(enum kmsg_dump_reason rea
+ 		if (dumper->max_reason && reason > dumper->max_reason)
+ 			continue;
+ 
+-		/* initialize iterator with data about the stored records */
+-		dumper->active = true;
++		/*
++		 * use a local copy to avoid modifying the
++		 * iterator used by any other cpus/contexts
++		 */
++		memcpy(&dumper_local, dumper, sizeof(dumper_local));
+ 
+-		kmsg_dump_rewind(dumper);
++		/* initialize iterator with data about the stored records */
++		dumper_local.active = true;
++		kmsg_dump_rewind(&dumper_local);
+ 
+ 		/* invoke dumper which will iterate over records */
+-		dumper->dump(dumper, reason);
+-
+-		/* reset iterator */
+-		dumper->active = false;
++		dumper_local.dump(&dumper_local, reason);
+ 	}
+ 	rcu_read_unlock();
+ }
+@@ -2951,9 +2952,7 @@ bool kmsg_dump_get_line(struct kmsg_dump
+ {
+ 	bool ret;
+ 
+-	mutex_lock(&kmsg_dump_lock);
+ 	ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
+-	mutex_unlock(&kmsg_dump_lock);
+ 
+ 	return ret;
+ }
+@@ -3105,9 +3104,7 @@ void kmsg_dump_rewind_nolock(struct kmsg
+  */
+ void kmsg_dump_rewind(struct kmsg_dumper *dumper)
+ {
+-	mutex_lock(&kmsg_dump_lock);
+ 	kmsg_dump_rewind_nolock(dumper);
+-	mutex_unlock(&kmsg_dump_lock);
+ }
+ EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
+