Adding upstream version 5.6.0.upstream/5.6.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/modules/detect_time_jump/detect_time_jump.lua b/modules/detect_time_jump/detect_time_jump.lua
new file mode 100644
index 0000000..6c5b63f
--- /dev/null
+++ b/modules/detect_time_jump/detect_time_jump.lua
@@ -0,0 +1,45 @@
+-- SPDX-License-Identifier: GPL-3.0-or-later
+-- Module interface
+local ffi = require('ffi')
+
+local mod = {}
+mod.threshold = 10 * min
+local event_id = nil
+
+-- Get time of last cache clear. Compute difference between realtime
+-- and monotonic time. Compute difference of actual realtime and monotonic
+-- time. In ideal case these differences should be almost same.
+-- If they differ more than mod.threshold value then clear cache.
+local function check_time()
+	local checkpoint = cache.checkpoint()
+	local cache_timeshift = checkpoint.walltime.sec * 1000 - checkpoint.monotime
+	local actual_timeshift = os.time() * 1000 - tonumber(ffi.C.kr_now())
+	local jump_backward = cache_timeshift - actual_timeshift
+	if jump_backward > mod.threshold then
+		log_info(ffi.C.LOG_GRP_DETECTTIMEJUMP, "Detected backwards time jump, clearing cache.\n" ..
+		"But what does that mean? It means your future hasn't been written yet."
+		)
+		cache.clear()
+	elseif -jump_backward > mod.threshold then
+		-- On Linux 4.17+ this shouldn't happen anymore: https://lwn.net/Articles/751482/
+		log_info(ffi.C.LOG_GRP_DETECTTIMEJUMP, "Detected forward time jump.  (Suspend-resume, possibly.)")
+		cache.checkpoint(true)
+	end
+end
+
+function mod.init()
+	if event_id then
+		error("Module is already loaded.")
+	else
+		event_id = event.recurrent(1 * min , check_time)
+	end
+end
+
+function mod.deinit()
+	if event_id then
+		event.cancel(event_id)
+		event_id = nil
+	end
+end
+
+return mod