[PATCH 2/3] Documentation: kmemleak: fix stale statements about scanning

[Breno Leitao <leitao@debian.org>]

Three statements in the "false positives/negatives" and "Limitations"
sections have never matched the code:

 - task stack scanning is on by default (kmemleak_stack_scan = 1), as
   the parameter list earlier in the same document already states;

 - MSECS_MIN_AGE has been 5000, not 1000, since the initial commit;

 - scanning is done by a periodic kthread. Reading the debugfs file
   only lists what the last scan found; kmemleak_open() calls
   seq_open() and never scans.

Fixes: 04f70336c80c ("kmemleak: Add documentation on the memory leak detector")
Fixes: e0a2a1601bec ("kmemleak: Enable task stacks scanning by default")
Signed-off-by: Breno Leitao <leitao@debian.org>
---
 Documentation/dev-tools/kmemleak.rst | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/Documentation/dev-tools/kmemleak.rst b/Documentation/dev-tools/kmemleak.rst
index 8dad7647742d3..b5fe7e671d0f8 100644
--- a/Documentation/dev-tools/kmemleak.rst
+++ b/Documentation/dev-tools/kmemleak.rst
@@ -190,7 +190,8 @@ reported by kmemleak because values found during the memory scanning
 point to such objects. To reduce the number of false negatives, kmemleak
 provides the kmemleak_ignore, kmemleak_scan_area, kmemleak_no_scan and
 kmemleak_erase functions (see above). The task stacks also increase the
-amount of false negatives and their scanning is not enabled by default.
+amount of false negatives and their scanning is enabled by default; it
+can be turned off with ``stack=off``.
 
 The false positives are objects wrongly reported as being memory leaks
 (orphan). For objects known not to be leaks, kmemleak provides the
@@ -200,7 +201,7 @@ longer be scanned.
 
 Some of the reported leaks are only transient, especially on SMP
 systems, because of pointers temporarily stored in CPU registers or
-stacks. Kmemleak defines MSECS_MIN_AGE (defaulting to 1000) representing
+stacks. Kmemleak defines MSECS_MIN_AGE (defaulting to 5000) representing
 the minimum age of an object to be reported as a memory leak.
 
 The ``min_unref_scans`` module parameter requires an object to be seen
@@ -217,8 +218,10 @@ Limitations and Drawbacks
 -------------------------
 
 The main drawback is the reduced performance of memory allocation and
-freeing. To avoid other penalties, the memory scanning is only performed
-when the /sys/kernel/debug/kmemleak file is read. Anyway, this tool is
+freeing. To avoid other penalties, the memory scanning is performed by a
+periodic thread rather than on every allocation. Reading the
+/sys/kernel/debug/kmemleak file only lists the objects found by the last
+scan; writing ``scan`` to it triggers a new one. Anyway, this tool is
 intended for debugging purposes where the performance might not be the
 most important requirement.
 

-- 
2.53.0-Meta