kernel/linux.git/include/linux/ref_tracker.h, branch v6.19.11

ref_tracker: eliminate the ref_tracker_dir name field

2025-06-20T00:02:04+00:00

Now that we have dentries and the ability to create meaningful symlinks to them, don't keep a name string in each tracker. Switch the output format to print "class@address", and drop the name field. Also, add a kerneldoc header for ref_tracker_dir_init(). Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20250618-reftrack-dbgfs-v15-9-24fc37ead144@kernel.org Signed-off-by: Jakub Kicinski

ref_tracker: add a way to create a symlink to the ref_tracker_dir debugfs file

2025-06-20T00:02:04+00:00

Add the ability for a subsystem to add a user-friendly symlink that points to a ref_tracker_dir's debugfs file. Add a separate debugfs_symlinks xarray and use that to track symlinks. The reaper workqueue job will remove symlinks before their corresponding dentries. Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20250618-reftrack-dbgfs-v15-7-24fc37ead144@kernel.org Signed-off-by: Jakub Kicinski

ref_tracker: automatically register a file in debugfs for a ref_tracker_dir

2025-06-20T00:02:04+00:00

Currently, there is no convenient way to see the info that the ref_tracking infrastructure collects. Attempt to create a file in debugfs when called from ref_tracker_dir_init(). The file is given the name "class@%px", as having the unmodified address is helpful for debugging. This should be safe since this directory is only accessible by root While ref_tracker_dir_init() is generally called from a context where sleeping is OK, ref_tracker_dir_exit() can be called from anywhere. Thus, dentry cleanup must be handled asynchronously. Add a new global xarray that has entries with the ref_tracker_dir pointer as the index and the corresponding debugfs dentry pointer as the value. Instead of removing the debugfs dentry, have ref_tracker_dir_exit() set a mark on the xarray entry and schedule a workqueue job. The workqueue job then walks the xarray looking for marked entries, and removes their xarray entries and the debugfs dentries. Because of this, the debugfs dentry can outlive the corresponding ref_tracker_dir. Have ref_tracker_debugfs_show() take extra care to ensure that it's safe to dereference the dir pointer before using it. Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20250618-reftrack-dbgfs-v15-6-24fc37ead144@kernel.org Signed-off-by: Jakub Kicinski

ref_tracker: add a static classname string to each ref_tracker_dir

2025-06-20T00:02:04+00:00

A later patch in the series will be adding debugfs files for each ref_tracker that get created in ref_tracker_dir_init(). The format will be "class@%px". The current "name" string can vary between ref_tracker_dir objects of the same type, so it's not suitable for this purpose. Add a new "class" string to the ref_tracker dir that describes the the type of object (sans any individual info for that object). Also, in the i915 driver, gate the creation of debugfs files on whether the dentry pointer is still set to NULL. CI has shown that the ref_tracker_dir can be initialized more than once. Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20250618-reftrack-dbgfs-v15-4-24fc37ead144@kernel.org Signed-off-by: Jakub Kicinski

ref_tracker: have callers pass output function to pr_ostream()

2025-06-20T00:02:03+00:00

In a later patch, we'll be adding a 3rd mechanism for outputting ref_tracker info via seq_file. Instead of a conditional, have the caller set a pointer to an output function in struct ostream. As part of this, the log prefix must be explicitly passed in, as it's too late for the pr_fmt macro. Reviewed-by: Andrew Lunn Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20250618-reftrack-dbgfs-v15-3-24fc37ead144@kernel.org Signed-off-by: Jakub Kicinski

lib/ref_tracker: add printing to memory buffer

2023-06-05T22:28:42+00:00

Similar to stack_(depot|trace)_snprint the patch adds helper to printing stats to memory buffer. It will be helpful in case of debugfs. Signed-off-by: Andrzej Hajda Reviewed-by: Andi Shyti Reviewed-by: Eric Dumazet Signed-off-by: Jakub Kicinski

lib/ref_tracker: improve printing stats

2023-06-05T22:28:42+00:00

In case the library is tracking busy subsystem, simply printing stack for every active reference will spam log with long, hard to read, redundant stack traces. To improve readabilty following changes have been made: - reports are printed per stack_handle - log is more compact, - added display name for ref_tracker_dir - it will differentiate multiple subsystems, - stack trace is printed indented, in the same printk call, - info about dropped references is printed as well. Signed-off-by: Andrzej Hajda Reviewed-by: Andi Shyti Reviewed-by: Eric Dumazet Signed-off-by: Jakub Kicinski

lib/ref_tracker: add unlocked leak print helper

2023-06-05T22:28:42+00:00

To have reliable detection of leaks, caller must be able to check under the same lock both: tracked counter and the leaks. dir.lock is natural candidate for such lock and unlocked print helper can be called with this lock taken. As a bonus we can reuse this helper in ref_tracker_dir_exit. Signed-off-by: Andrzej Hajda Reviewed-by: Andi Shyti Reviewed-by: Eric Dumazet Signed-off-by: Jakub Kicinski

ref_tracker: add a count of untracked references

2022-02-05T15:22:44+00:00

We are still chasing a netdev refcount imbalance, and we suspect we have one rogue dev_put() that is consuming a reference taken from a dev_hold_track() To detect this case, allow ref_tracker_alloc() and ref_tracker_free() to be called with a NULL @trackerp parameter, and use a dedicated refcount_t just for them. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

ref_tracker: implement use-after-free detection

2022-02-05T15:22:44+00:00

Whenever ref_tracker_dir_init() is called, mark the struct ref_tracker_dir as dead. Test the dead status from ref_tracker_alloc() and ref_tracker_free() This should detect buggy dev_put()/dev_hold() happening too late in netdevice dismantle process. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller