src/bin/lttng-sessiond/health.h

   1 /*
   2  * Copyright (C) 2012 - David Goulet <dgoulet@efficios.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License, version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  11  * more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along with
  14  * this program; if not, write to the Free Software Foundation, Inc., 51
  15  * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #ifndef _HEALTH_H
  19 #define _HEALTH_H
  20
  21 #include <assert.h>
  22 #include <time.h>
  23 #include <pthread.h>
  24 #include <urcu/tls-compat.h>
  25 #include <urcu/uatomic.h>
  26 #include <urcu/list.h>
  27
  28 /*
  29  * These are the value added to the current state depending of the position in
  30  * the thread where is either waiting on a poll() or running in the code.
  31  */
  32 #define HEALTH_POLL_VALUE       (1UL << 0)
  33 #define HEALTH_CODE_VALUE       (1UL << 1)
  34
  35 #define HEALTH_IS_IN_POLL(x)    ((x) & HEALTH_POLL_VALUE)
  36
  37 enum health_flags {
  38         HEALTH_ERROR = (1U << 0),
  39 };
  40
  41 enum health_type {
  42         HEALTH_TYPE_CMD                 = 0,
  43         HEALTH_TYPE_APP_MANAGE  = 1,
  44         HEALTH_TYPE_APP_REG             = 2,
  45         HEALTH_TYPE_KERNEL              = 3,
  46         HEALTH_TYPE_CONSUMER    = 4,
  47
  48         HEALTH_NUM_TYPE,
  49 };
  50
  51 struct health_tls_state_list {
  52         struct cds_list_head head;
  53 };
  54
  55 struct health_state {
  56         /*
  57          * last counter and last_time are only read and updated by the health_check
  58          * thread (single updater).
  59          */
  60         unsigned long last;
  61         struct timespec last_time;
  62
  63         /*
  64          * current and flags are updated by multiple threads concurrently.
  65          */
  66         unsigned long current;          /* progress counter, updated atomically */
  67         enum health_flags flags;        /* other flags, updated atomically */
  68         enum health_type type;          /* Indicates the nature of the thread. */
  69         /* Node of the global TLS state list. */
  70         struct cds_list_head node;
  71 };
  72
  73 /* Declare TLS health state. */
  74 extern DECLARE_URCU_TLS(struct health_state, health_state);
  75
  76 /*
  77  * Update current counter by 1 to indicate that the thread entered or left a
  78  * blocking state caused by a poll(). If the counter's value is not an even
  79  * number (meaning a code execution flow), an assert() is raised.
  80  */
  81 static inline void health_poll_entry(void)
  82 {
  83         /* Code MUST be in code execution state which is an even number. */
  84         assert(!(uatomic_read(&URCU_TLS(health_state).current)
  85                                 & HEALTH_POLL_VALUE));
  86
  87         uatomic_add(&URCU_TLS(health_state).current, HEALTH_POLL_VALUE);
  88 }
  89
  90 /*
  91  * Update current counter by 1 indicating the exit of a poll or blocking call.
  92  * If the counter's value is not an odd number (a poll execution), an assert()
  93  * is raised.
  94  */
  95 static inline void health_poll_exit(void)
  96 {
  97         /* Code MUST be in poll execution state which is an odd number. */
  98         assert(uatomic_read(&URCU_TLS(health_state).current)
  99                                 & HEALTH_POLL_VALUE);
 100
 101         uatomic_add(&URCU_TLS(health_state).current, HEALTH_POLL_VALUE);
 102 }
 103
 104 /*
 105  * Update current counter by 2 indicates progress in execution of a
 106  * thread.
 107  */
 108 static inline void health_code_update(void)
 109 {
 110         uatomic_add(&URCU_TLS(health_state).current, HEALTH_CODE_VALUE);
 111 }
 112
 113 /*
 114  * Set health "error" flag.
 115  */
 116 static inline void health_error(void)
 117 {
 118         uatomic_or(&URCU_TLS(health_state).flags, HEALTH_ERROR);
 119 }
 120
 121 int health_check_state(enum health_type type);
 122 void health_register(enum health_type type);
 123 void health_unregister(void);
 124
 125 #endif /* _HEALTH_H */