5.4-stable patches

added patches:
	ring-buffer-fix-wake-ups-when-buffer_percent-is-set-to-100.patch

diff --git a/queue-5.4/ring-buffer-fix-wake-ups-when-buffer_percent-is-set-to-100.patch b/queue-5.4/ring-buffer-fix-wake-ups-when-buffer_percent-is-set-to-100.patch
new file mode 100644 (file)
index 0000000..7980dc4
--- /dev/null
+++ b/queue-5.4/ring-buffer-fix-wake-ups-when-buffer_percent-is-set-to-100.patch
@@ -0,0 +1,73 @@
+From 623b1f896fa8a669a277ee5a258307a16c7377a3 Mon Sep 17 00:00:00 2001
+From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
+Date: Tue, 26 Dec 2023 12:59:02 -0500
+Subject: ring-buffer: Fix wake ups when buffer_percent is set to 100
+
+From: Steven Rostedt (Google) <rostedt@goodmis.org>
+
+commit 623b1f896fa8a669a277ee5a258307a16c7377a3 upstream.
+
+The tracefs file "buffer_percent" is to allow user space to set a
+water-mark on how much of the tracing ring buffer needs to be filled in
+order to wake up a blocked reader.
+
+ 0 - is to wait until any data is in the buffer
+ 1 - is to wait for 1% of the sub buffers to be filled
+ 50 - would be half of the sub buffers are filled with data
+ 100 - is not to wake the waiter until the ring buffer is completely full
+
+Unfortunately the test for being full was:
+
+       dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
+       return (dirty * 100) > (full * nr_pages);
+
+Where "full" is the value for "buffer_percent".
+
+There is two issues with the above when full == 100.
+
+1. dirty * 100 > 100 * nr_pages will never be true
+   That is, the above is basically saying that if the user sets
+   buffer_percent to 100, more pages need to be dirty than exist in the
+   ring buffer!
+
+2. The page that the writer is on is never considered dirty, as dirty
+   pages are only those that are full. When the writer goes to a new
+   sub-buffer, it clears the contents of that sub-buffer.
+
+That is, even if the check was ">=" it would still not be equal as the
+most pages that can be considered "dirty" is nr_pages - 1.
+
+To fix this, add one to dirty and use ">=" in the compare.
+
+Link: https://lore.kernel.org/linux-trace-kernel/20231226125902.4a057f1d@gandalf.local.home
+
+Cc: stable@vger.kernel.org
+Cc: Mark Rutland <mark.rutland@arm.com>
+Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
+Fixes: 03329f9939781 ("tracing: Add tracefs file buffer_percentage")
+Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ kernel/trace/ring_buffer.c |    9 +++++++--
+ 1 file changed, 7 insertions(+), 2 deletions(-)
+
+--- a/kernel/trace/ring_buffer.c
++++ b/kernel/trace/ring_buffer.c
+@@ -579,9 +579,14 @@ static __always_inline bool full_hit(str
+       if (!nr_pages || !full)
+               return true;
+ 
+-      dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
++      /*
++       * Add one as dirty will never equal nr_pages, as the sub-buffer
++       * that the writer is on is not counted as dirty.
++       * This is needed if "buffer_percent" is set to 100.
++       */
++      dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
+ 
+-      return (dirty * 100) > (full * nr_pages);
++      return (dirty * 100) >= (full * nr_pages);
+ }
+ 
+ /*

diff --git a/queue-5.4/series b/queue-5.4/series
index 5a091c30cb34082b985d51dd01cab71b77e1db7f..9bfe5014fe99d5557a7303a0e565df273dc7c64b 100644 (file)
--- a/queue-5.4/series
+++ b/queue-5.4/series
@@ -43,3 +43,4 @@ usb-fotg210-hcd-delete-an-incorrect-bounds-test.patch
 smb-client-fix-oob-in-smbcalcsize.patch
 bus-ti-sysc-use-fsleep-instead-of-usleep_range-in-sy.patch
 bus-ti-sysc-flush-posted-write-only-after-srst_udela.patch
+ring-buffer-fix-wake-ups-when-buffer_percent-is-set-to-100.patch