src/common/defaults.cpp

   1 /*
   2  * Copyright (C) 2012 EfficiOS Inc.
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #define _LGPL_SOURCE
   9 #include "defaults.hpp"
  10 #include "error.hpp"
  11 #include "macros.hpp"
  12
  13 #include <algorithm>
  14 #include <pthread.h>
  15 #include <stdbool.h>
  16 #include <stddef.h>
  17 #include <sys/resource.h>
  18 #include <unistd.h>
  19
  20 static int pthread_attr_init_done;
  21 static pthread_attr_t tattr;
  22
  23 static size_t get_page_size()
  24 {
  25         const long ret = sysconf(_SC_PAGE_SIZE);
  26
  27         if (ret < 0) {
  28                 /*
  29                  * Fatal error since there is no safe way to recover from this.
  30                  */
  31                 PERROR("Failed to get system page size using sysconf(_SC_PAGE_SIZE)");
  32                 abort();
  33         }
  34
  35         return (size_t) ret;
  36 }
  37
  38 size_t default_get_channel_subbuf_size()
  39 {
  40         return std::max<size_t>(_DEFAULT_CHANNEL_SUBBUF_SIZE, get_page_size());
  41 }
  42
  43 size_t default_get_metadata_subbuf_size()
  44 {
  45         return std::max<size_t>(DEFAULT_METADATA_SUBBUF_SIZE, get_page_size());
  46 }
  47
  48 size_t default_get_kernel_channel_subbuf_size()
  49 {
  50         return std::max<size_t>(DEFAULT_KERNEL_CHANNEL_SUBBUF_SIZE, get_page_size());
  51 }
  52
  53 size_t default_get_ust_pid_channel_subbuf_size()
  54 {
  55         return std::max<size_t>(DEFAULT_UST_PID_CHANNEL_SUBBUF_SIZE, get_page_size());
  56 }
  57
  58 size_t default_get_ust_uid_channel_subbuf_size()
  59 {
  60         return std::max<size_t>(DEFAULT_UST_UID_CHANNEL_SUBBUF_SIZE, get_page_size());
  61 }
  62
  63 pthread_attr_t *default_pthread_attr()
  64 {
  65         if (pthread_attr_init_done) {
  66                 return &tattr;
  67         }
  68
  69         WARN("Uninitialized pthread attributes, using libc defaults.");
  70         return nullptr;
  71 }
  72
  73 static void __attribute__((constructor)) init_default_pthread_attr()
  74 {
  75         int ret;
  76         struct rlimit rlim;
  77         size_t pthread_ss, system_ss, selected_ss;
  78
  79         ret = pthread_attr_init(&tattr);
  80         if (ret) {
  81                 errno = ret;
  82                 PERROR("pthread_attr_init");
  83                 goto error;
  84         }
  85
  86         /* Get system stack size limits. */
  87         ret = getrlimit(RLIMIT_STACK, &rlim);
  88         if (ret < 0) {
  89                 PERROR("getrlimit");
  90                 goto error_destroy;
  91         }
  92         DBG("Stack size limits: soft %lld, hard %lld bytes",
  93             (long long) rlim.rlim_cur,
  94             (long long) rlim.rlim_max);
  95
  96         /*
  97          * getrlimit() may return a stack size of "-1", meaning "unlimited".
  98          * In this case, we impose a known-good default minimum value which will
  99          * override the libc's default stack size if it is smaller.
 100          */
 101         system_ss = rlim.rlim_cur != -1 ? rlim.rlim_cur : DEFAULT_LTTNG_THREAD_STACK_SIZE;
 102
 103         /* Get pthread default thread stack size. */
 104         ret = pthread_attr_getstacksize(&tattr, &pthread_ss);
 105         if (ret < 0) {
 106                 PERROR("pthread_attr_getstacksize");
 107                 goto error_destroy;
 108         }
 109         DBG("Default pthread stack size is %zu bytes", pthread_ss);
 110
 111         selected_ss = std::max(pthread_ss, system_ss);
 112         if (selected_ss < DEFAULT_LTTNG_THREAD_STACK_SIZE) {
 113                 DBG("Default stack size is too small, setting it to %zu bytes",
 114                     (size_t) DEFAULT_LTTNG_THREAD_STACK_SIZE);
 115                 selected_ss = DEFAULT_LTTNG_THREAD_STACK_SIZE;
 116         }
 117
 118         if (rlim.rlim_max > 0 && selected_ss > rlim.rlim_max) {
 119                 WARN("Your system's stack size restrictions (%zu bytes) may be too low for the LTTng daemons to function properly, please set the stack size limit to at least %zu bytes to ensure reliable operation",
 120                      (size_t) rlim.rlim_max,
 121                      (size_t) DEFAULT_LTTNG_THREAD_STACK_SIZE);
 122                 selected_ss = (size_t) rlim.rlim_max;
 123         }
 124
 125         ret = pthread_attr_setstacksize(&tattr, selected_ss);
 126         if (ret < 0) {
 127                 PERROR("pthread_attr_setstacksize");
 128                 goto error_destroy;
 129         }
 130         pthread_attr_init_done = 1;
 131 error:
 132         return;
 133 error_destroy:
 134         ret = pthread_attr_destroy(&tattr);
 135         if (ret) {
 136                 errno = ret;
 137                 PERROR("pthread_attr_destroy");
 138         }
 139 }
 140
 141 static void __attribute__((destructor)) fini_default_pthread_attr()
 142 {
 143         int ret;
 144
 145         if (!pthread_attr_init_done) {
 146                 return;
 147         }
 148
 149         ret = pthread_attr_destroy(&tattr);
 150         if (ret) {
 151                 errno = ret;
 152                 PERROR("pthread_attr_destroy");
 153         }
 154 }