From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- Documentation/block/stat.rst | 103 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) create mode 100644 Documentation/block/stat.rst (limited to 'Documentation/block/stat.rst') diff --git a/Documentation/block/stat.rst b/Documentation/block/stat.rst new file mode 100644 index 000000000..a1cd9db20 --- /dev/null +++ b/Documentation/block/stat.rst @@ -0,0 +1,103 @@ +=============================================== +Block layer statistics in /sys/block//stat +=============================================== + +This file documents the contents of the /sys/block//stat file. + +The stat file provides several statistics about the state of block +device . + +Q. + Why are there multiple statistics in a single file? Doesn't sysfs + normally contain a single value per file? + +A. + By having a single file, the kernel can guarantee that the statistics + represent a consistent snapshot of the state of the device. If the + statistics were exported as multiple files containing one statistic + each, it would be impossible to guarantee that a set of readings + represent a single point in time. + +The stat file consists of a single line of text containing 17 decimal +values separated by whitespace. The fields are summarized in the +following table, and described in more detail below. + + +=============== ============= ================================================= +Name units description +=============== ============= ================================================= +read I/Os requests number of read I/Os processed +read merges requests number of read I/Os merged with in-queue I/O +read sectors sectors number of sectors read +read ticks milliseconds total wait time for read requests +write I/Os requests number of write I/Os processed +write merges requests number of write I/Os merged with in-queue I/O +write sectors sectors number of sectors written +write ticks milliseconds total wait time for write requests +in_flight requests number of I/Os currently in flight +io_ticks milliseconds total time this block device has been active +time_in_queue milliseconds total wait time for all requests +discard I/Os requests number of discard I/Os processed +discard merges requests number of discard I/Os merged with in-queue I/O +discard sectors sectors number of sectors discarded +discard ticks milliseconds total wait time for discard requests +flush I/Os requests number of flush I/Os processed +flush ticks milliseconds total wait time for flush requests +=============== ============= ================================================= + +read I/Os, write I/Os, discard I/0s +=================================== + +These values increment when an I/O request completes. + +flush I/Os +========== + +These values increment when an flush I/O request completes. + +Block layer combines flush requests and executes at most one at a time. +This counts flush requests executed by disk. Not tracked for partitions. + +read merges, write merges, discard merges +========================================= + +These values increment when an I/O request is merged with an +already-queued I/O request. + +read sectors, write sectors, discard_sectors +============================================ + +These values count the number of sectors read from, written to, or +discarded from this block device. The "sectors" in question are the +standard UNIX 512-byte sectors, not any device- or filesystem-specific +block size. The counters are incremented when the I/O completes. + +read ticks, write ticks, discard ticks, flush ticks +=================================================== + +These values count the number of milliseconds that I/O requests have +waited on this block device. If there are multiple I/O requests waiting, +these values will increase at a rate greater than 1000/second; for +example, if 60 read requests wait for an average of 30 ms, the read_ticks +field will increase by 60*30 = 1800. + +in_flight +========= + +This value counts the number of I/O requests that have been issued to +the device driver but have not yet completed. It does not include I/O +requests that are in the queue but not yet issued to the device driver. + +io_ticks +======== + +This value counts the number of milliseconds during which the device has +had I/O requests queued. + +time_in_queue +============= + +This value counts the number of milliseconds that I/O requests have waited +on this block device. If there are multiple I/O requests waiting, this +value will increase as the product of the number of milliseconds times the +number of requests waiting (see "read ticks" above for an example). -- cgit v1.3.1