Merge tag 'trace-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from

 - allow module init functions to be traced

 - clean up some unused or not used by config events (saves space)

 - clean up of trace histogram code

 - add support for preempt and interrupt enabled/disable events

 - other various clean ups

* tag 'trace-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (30 commits)
  tracing, thermal: Hide cpu cooling trace events when not in use
  tracing, thermal: Hide devfreq trace events when not in use
  ftrace: Kill FTRACE_OPS_FL_PER_CPU
  perf/ftrace: Small cleanup
  perf/ftrace: Fix function trace events
  perf/ftrace: Revert ("perf/ftrace: Fix double traces of perf on ftrace:function")
  tracing, dma-buf: Remove unused trace event dma_fence_annotate_wait_on
  tracing, memcg, vmscan: Hide trace events when not in use
  tracing/xen: Hide events that are not used when X86_PAE is not defined
  tracing: mark trace_test_buffer as __maybe_unused
  printk: Remove superfluous memory barriers from printk_safe
  ftrace: Clear hashes of stale ips of init memory
  tracing: Add support for preempt and irq enable/disable events
  tracing: Prepare to add preempt and irq trace events
  ftrace/kallsyms: Have /proc/kallsyms show saved mod init functions
  ftrace: Add freeing algorithm to free ftrace_mod_maps
  ftrace: Save module init functions kallsyms symbols for tracing
  ftrace: Allow module init functions to be traced
  ftrace: Add a ftrace_free_mem() function for modules to use
  tracing: Reimplement log2
  ...

1 files changed, 8 insertions, 7 deletions

diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 3cdaeaef9ce1..724d9292d4b9 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -39,7 +39,7 @@
  * There are situations when we want to make sure that all buffers
  * were handled or when IRQs are blocked.
  */
-static int printk_safe_irq_ready;
+static int printk_safe_irq_ready __read_mostly;
 
 #define SAFE_LOG_BUF_LEN ((1 << CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT) -	\
 				sizeof(atomic_t) -			\
@@ -63,11 +63,8 @@ static DEFINE_PER_CPU(struct printk_safe_seq_buf, nmi_print_seq);
 /* Get flushed in a more safe context. */
 static void queue_flush_work(struct printk_safe_seq_buf *s)
 {
-	if (printk_safe_irq_ready) {
-		/* Make sure that IRQ work is really initialized. */
-		smp_rmb();
+	if (printk_safe_irq_ready)
 		irq_work_queue(&s->work);
-	}
 }
 
 /*
@@ -398,8 +395,12 @@ void __init printk_safe_init(void)
 #endif
 	}
 
-	/* Make sure that IRQ works are initialized before enabling. */
-	smp_wmb();
+	/*
+	 * In the highly unlikely event that a NMI were to trigger at
+	 * this moment. Make sure IRQ work is set up before this
+	 * variable is set.
+	 */
+	barrier();
 	printk_safe_irq_ready = 1;
 
 	/* Flush pending messages that did not have scheduled IRQ works. */