mainlining shenanigans
a35873a099
Currently, tracing snapshots are context-free - they capture the ring buffer contents at the time the tracing_snapshot() function was invoked, and nothing else. Additionally, they're always taken unconditionally - the calling code can decide whether or not to take a snapshot, but the data used to make that decision is kept separately from the snapshot itself. This change adds the ability to associate with each trace instance some user data, along with an 'update' function that can use that data to determine whether or not to actually take a snapshot. The update function can then update that data along with any other state (as part of the data presumably), if warranted. Because snapshots are 'global' per-instance, only one user can enable and use a conditional snapshot for any given trace instance. To enable a conditional snapshot (see details in the function and data structure comments), the user calls tracing_snapshot_cond_enable(). Similarly, to disable a conditional snapshot and free it up for other users, tracing_snapshot_cond_disable() should be called. To actually initiate a conditional snapshot, tracing_snapshot_cond() should be called. tracing_snapshot_cond() will invoke the update() callback, allowing the user to decide whether or not to actually take the snapshot and update the user-defined data associated with the snapshot. If the callback returns 'true', tracing_snapshot_cond() will then actually take the snapshot and return. This scheme allows for flexibility in snapshot implementations - for example, by implementing slightly different update() callbacks, snapshots can be taken in situations where the user is only interested in taking a snapshot when a new maximum in hit versus when a value changes in any way at all. Future patches will demonstrate both cases. Link: http://lkml.kernel.org/r/1bea07828d5fd6864a585f83b1eed47ce097eb45.1550100284.git.tom.zanussi@linux.intel.com Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.