Merge 4.4.277 into android-4.4-p

Changes in 4.4.277
	ARM: brcmstb: dts: fix NAND nodes names
	ARM: dts: BCM63xx: Fix NAND nodes names
	ARM: dts: imx6: phyFLEX: Fix UART hardware flow control
	ARM: imx: pm-imx5: Fix references to imx5_cpu_suspend_info
	thermal/core: Correct function name thermal_zone_device_unregister()
	kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set
	scsi: aic7xxx: Fix unintentional sign extension issue on left shift of u8
	sched/fair: Fix CFS bandwidth hrtimer expiry type
	Revert "memory: fsl_ifc: fix leak of IO mapping on probe failure"
	x86/fpu: Make init_fpstate correct with optimized XSAVE
	net: ipv6: fix return value of ip6_skb_dst_mtu
	net: bcmgenet: Ensure all TX/RX queues DMAs are disabled
	net: moxa: fix UAF in moxart_mac_probe
	net: ti: fix UAF in tlan_remove_one
	net: validate lwtstate->data before returning from skb_tunnel_info()
	tcp: annotate data races around tp->mtu_info
	ipv6: tcp: drop silly ICMPv6 packet too big messages
	iavf: Fix an error handling path in 'iavf_probe()'
	igb: Check if num of q_vectors is smaller than max before array access
	perf test bpf: Free obj_buf
	perf probe-file: Delete namelist in del_events() on the error path
	s390/bpf: Perform r1 range checking before accessing jit->seen_reg[r1]
	net: fix uninit-value in caif_seqpkt_sendmsg
	net: decnet: Fix sleeping inside in af_decnet
	netrom: Decrease sock refcount when sock timers expire
	scsi: iscsi: Fix iface sysfs attr detection
	scsi: target: Fix protect handling in WRITE SAME(32)
	Revert "USB: quirks: ignore remote wake-up on Fibocom L850-GL LTE modem"
	proc: Avoid mixing integer types in mem_rw()
	s390/ftrace: fix ftrace_update_ftrace_func implementation
	ALSA: sb: Fix potential ABBA deadlock in CSP driver
	xhci: Fix lost USB 2 remote wake
	KVM: PPC: Book3S: Fix H_RTAS rets buffer overflow
	usb: hub: Disable USB 3 device initiated lpm if exit latency is too high
	USB: usb-storage: Add LaCie Rugged USB3-FW to IGNORE_UAS
	usb: max-3421: Prevent corruption of freed memory
	usb: renesas_usbhs: Fix superfluous irqs happen after usb_pkt_pop()
	USB: serial: option: add support for u-blox LARA-R6 family
	USB: serial: cp210x: fix comments for GE CS1000
	USB: serial: cp210x: add ID for CEL EM3588 USB ZigBee stick
	tracing: Fix bug in rb_per_cpu_empty() that might cause deadloop.
	media: ngene: Fix out-of-bounds bug in ngene_command_config_free_buf()
	net: bcmgenet: ensure EXT_ENERGY_DET_MASK is clear
	iio: accel: bma180: Use explicit member assignment
	iio: accel: bma180: Fix BMA25x bandwidth register values
	btrfs: compression: don't try to compress if we don't have enough pages
	Linux 4.4.277

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I7159a9fb5545e504222fcee566c6661c1070c8f7

1 files changed, 24 insertions, 4 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 1ec760f6bf58..19b30ff90cc4 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3086,10 +3086,30 @@ static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
 	if (unlikely(!head))
 		return true;
 
-	return reader->read == rb_page_commit(reader) &&
-		(commit == reader ||
-		 (commit == head &&
-		  head->read == rb_page_commit(commit)));
+	/* Reader should exhaust content in reader page */
+	if (reader->read != rb_page_commit(reader))
+		return false;
+
+	/*
+	 * If writers are committing on the reader page, knowing all
+	 * committed content has been read, the ring buffer is empty.
+	 */
+	if (commit == reader)
+		return true;
+
+	/*
+	 * If writers are committing on a page other than reader page
+	 * and head page, there should always be content to read.
+	 */
+	if (commit != head)
+		return false;
+
+	/*
+	 * Writers are committing on the head page, we just need
+	 * to care about there're committed data, and the reader will
+	 * swap reader page with head page when it is to read data.
+	 */
+	return rb_page_commit(commit) == 0;
 }
 
 /**