Commit 49b393af authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

perf: Add comment to enum perf_event_state 



Better describe the event states.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarLeo Yan <leo.yan@arm.com>
Link: https://lkml.kernel.org/r/20250604135801.GK38114@noisy.programming.kicks-ass.net
parent 3172fb98

include/linux/perf_event.h

+40 −2
Original line number Diff line number Diff line
@@ -635,8 +635,46 @@ struct perf_addr_filter_range { 
	unsigned long			size;

};



/**

 * enum perf_event_state - the states of an event:

/*

 * The normal states are:

 *

 *            ACTIVE    --.

 *               ^        |

 *               |        |

 *       sched_{in,out}() |

 *               |        |

 *               v        |

 *      ,---> INACTIVE  --+ <-.

 *      |                 |   |

 *      |                {dis,en}able()

 *   sched_in()           |   |

 *      |       OFF    <--' --+

 *      |                     |

 *      `--->  ERROR    ------'

 *

 * That is:

 *

 * sched_in:       INACTIVE          -> {ACTIVE,ERROR}

 * sched_out:      ACTIVE            -> INACTIVE

 * disable:        {ACTIVE,INACTIVE} -> OFF

 * enable:         {OFF,ERROR}       -> INACTIVE

 *

 * Where {OFF,ERROR} are disabled states.

 *

 * Then we have the {EXIT,REVOKED,DEAD} states which are various shades of

 * defunct events:

 *

 *  - EXIT means task that the even was assigned to died, but child events

 *    still live, and further children can still be created. But the event

 *    itself will never be active again. It can only transition to

 *    {REVOKED,DEAD};

 *

 *  - REVOKED means the PMU the event was associated with is gone; all

 *    functionality is stopped but the event is still alive. Can only

 *    transition to DEAD;

 *

 *  - DEAD event really is DYING tearing down state and freeing bits.

 *

 */

enum perf_event_state {

	PERF_EVENT_STATE_DEAD		= -5,