Merge branch 'android-4.4-p' of https://android.googlesource.com/kernel/common into lineage-18.1-caf-msm8998

# By Pavel Skripkin (6) and others
# Via Greg Kroah-Hartman
* android-4.4-p:
  Linux 4.4.278
  sis900: Fix missing pci_disable_device() in probe and remove
  tulip: windbond-840: Fix missing pci_disable_device() in probe and remove
  net: llc: fix skb_over_panic
  mlx4: Fix missing error code in mlx4_load_one()
  tipc: fix sleeping in tipc accept routine
  netfilter: nft_nat: allow to specify layer 4 protocol NAT only
  cfg80211: Fix possible memory leak in function cfg80211_bss_update
  x86/asm: Ensure asm/proto.h can be included stand-alone
  NIU: fix incorrect error return, missed in previous revert
  can: esd_usb2: fix memory leak
  can: ems_usb: fix memory leak
  can: usb_8dev: fix memory leak
  ocfs2: issue zeroout to EOF blocks
  ocfs2: fix zero out valid data
  ARM: ensure the signal page contains defined contents
  lib/string.c: add multibyte memset functions
  ARM: dts: versatile: Fix up interrupt controller node names
  hfs: add lock nesting notation to hfs_find_init
  hfs: fix high memory mapping in hfs_bnode_read
  hfs: add missing clean-up in hfs_fill_super
  sctp: move 198 addresses from unusable to private scope
  net/802/garp: fix memleak in garp_request_join()
  net/802/mrp: fix memleak in mrp_request_join()
  workqueue: fix UAF in pwq_unbound_release_workfn()
  af_unix: fix garbage collect vs MSG_PEEK
  net: split out functions related to registering inflight socket files
  Linux 4.4.277
  btrfs: compression: don't try to compress if we don't have enough pages
  iio: accel: bma180: Fix BMA25x bandwidth register values
  iio: accel: bma180: Use explicit member assignment
  net: bcmgenet: ensure EXT_ENERGY_DET_MASK is clear
  media: ngene: Fix out-of-bounds bug in ngene_command_config_free_buf()
  tracing: Fix bug in rb_per_cpu_empty() that might cause deadloop.
  USB: serial: cp210x: add ID for CEL EM3588 USB ZigBee stick
  USB: serial: cp210x: fix comments for GE CS1000
  USB: serial: option: add support for u-blox LARA-R6 family
  usb: renesas_usbhs: Fix superfluous irqs happen after usb_pkt_pop()
  usb: max-3421: Prevent corruption of freed memory
  USB: usb-storage: Add LaCie Rugged USB3-FW to IGNORE_UAS
  usb: hub: Disable USB 3 device initiated lpm if exit latency is too high
  KVM: PPC: Book3S: Fix H_RTAS rets buffer overflow
  xhci: Fix lost USB 2 remote wake
  ALSA: sb: Fix potential ABBA deadlock in CSP driver
  s390/ftrace: fix ftrace_update_ftrace_func implementation
  proc: Avoid mixing integer types in mem_rw()
  Revert "USB: quirks: ignore remote wake-up on Fibocom L850-GL LTE modem"
  scsi: target: Fix protect handling in WRITE SAME(32)
  scsi: iscsi: Fix iface sysfs attr detection
  netrom: Decrease sock refcount when sock timers expire
  net: decnet: Fix sleeping inside in af_decnet
  net: fix uninit-value in caif_seqpkt_sendmsg
  s390/bpf: Perform r1 range checking before accessing jit->seen_reg[r1]
  perf probe-file: Delete namelist in del_events() on the error path
  perf test bpf: Free obj_buf
  igb: Check if num of q_vectors is smaller than max before array access
  iavf: Fix an error handling path in 'iavf_probe()'
  ipv6: tcp: drop silly ICMPv6 packet too big messages
  tcp: annotate data races around tp->mtu_info
  net: validate lwtstate->data before returning from skb_tunnel_info()
  net: ti: fix UAF in tlan_remove_one
  net: moxa: fix UAF in moxart_mac_probe
  net: bcmgenet: Ensure all TX/RX queues DMAs are disabled
  net: ipv6: fix return value of ip6_skb_dst_mtu
  x86/fpu: Make init_fpstate correct with optimized XSAVE
  Revert "memory: fsl_ifc: fix leak of IO mapping on probe failure"
  sched/fair: Fix CFS bandwidth hrtimer expiry type
  scsi: aic7xxx: Fix unintentional sign extension issue on left shift of u8
  kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set
  thermal/core: Correct function name thermal_zone_device_unregister()
  ARM: imx: pm-imx5: Fix references to imx5_cpu_suspend_info
  ARM: dts: imx6: phyFLEX: Fix UART hardware flow control
  ARM: dts: BCM63xx: Fix NAND nodes names
  ARM: brcmstb: dts: fix NAND nodes names

Change-Id: Id59b93b8704270f45923f262facbadde4c486a15

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;
 }
 
 /**