1 /* Stack cache management for NPTL.
2 Copyright (C) 2002-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19 #include <nptl-stack.h>
20 #include <ldsodefs.h>
21 #include <pthreadP.h>
22
23 size_t __nptl_stack_cache_maxsize = 40 * 1024 * 1024;
24 int32_t __nptl_stack_hugetlb = 1;
25
26 void
27 __nptl_stack_list_del (list_t *elem)
28 {
29 GL (dl_in_flight_stack) = (uintptr_t) elem;
30
31 atomic_write_barrier ();
32
33 list_del (elem);
34
35 atomic_write_barrier ();
36
37 GL (dl_in_flight_stack) = 0;
38 }
39 libc_hidden_def (__nptl_stack_list_del)
40
41 void
42 __nptl_stack_list_add (list_t *elem, list_t *list)
43 {
44 GL (dl_in_flight_stack) = (uintptr_t) elem | 1;
45
46 atomic_write_barrier ();
47
48 list_add (elem, list);
49
50 atomic_write_barrier ();
51
52 GL (dl_in_flight_stack) = 0;
53 }
54 libc_hidden_def (__nptl_stack_list_add)
55
56 void
57 __nptl_free_stacks (size_t limit)
58 {
59 /* We reduce the size of the cache. Remove the last entries until
60 the size is below the limit. */
61 list_t *entry;
62 list_t *prev;
63
64 /* Search from the end of the list. */
65 list_for_each_prev_safe (entry, prev, &GL (dl_stack_cache))
66 {
67 struct pthread *curr;
68
69 curr = list_entry (entry, struct pthread, list);
70 if (__nptl_stack_in_use (curr))
71 {
72 /* Unlink the block. */
73 __nptl_stack_list_del (entry);
74
75 /* Account for the freed memory. */
76 GL (dl_stack_cache_actsize) -= curr->stackblock_size;
77
78 /* Free the memory associated with the ELF TLS. */
79 _dl_deallocate_tls (TLS_TPADJ (curr), false);
80
81 /* Remove this block. This should never fail. If it does
82 something is really wrong. */
83 if (__munmap (curr->stackblock, curr->stackblock_size) != 0)
84 abort ();
85
86 /* Maybe we have freed enough. */
87 if (GL (dl_stack_cache_actsize) <= limit)
88 break;
89 }
90 }
91 }
92
93 /* Add a stack frame which is not used anymore to the stack. Must be
94 called with the cache lock held. */
95 static inline void
96 __attribute ((always_inline))
97 queue_stack (struct pthread *stack)
98 {
99 /* We unconditionally add the stack to the list. The memory may
100 still be in use but it will not be reused until the kernel marks
101 the stack as not used anymore. */
102 __nptl_stack_list_add (&stack->list, &GL (dl_stack_cache));
103
104 GL (dl_stack_cache_actsize) += stack->stackblock_size;
105 if (__glibc_unlikely (GL (dl_stack_cache_actsize)
106 > __nptl_stack_cache_maxsize))
107 __nptl_free_stacks (__nptl_stack_cache_maxsize);
108 }
109
110 void
111 __nptl_deallocate_stack (struct pthread *pd)
112 {
113 lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
114
115 /* Remove the thread from the list of threads with user defined
116 stacks. */
117 __nptl_stack_list_del (&pd->list);
118
119 /* Not much to do. Just free the mmap()ed memory. Note that we do
120 not reset the 'used' flag in the 'tid' field. This is done by
121 the kernel. If no thread has been created yet this field is
122 still zero. */
123 if (__glibc_likely (! pd->user_stack))
124 (void) queue_stack (pd);
125 else
126 /* Free the memory associated with the ELF TLS. */
127 _dl_deallocate_tls (TLS_TPADJ (pd), false);
128
129 lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
130 }
131 libc_hidden_def (__nptl_deallocate_stack)
132
133 /* This function is internal (it has a GLIBC_PRIVATE) version, but it
134 is widely used (either via weak symbol, or dlsym) to obtain the
135 __static_tls_size value. This value is then used to adjust the
136 value of the stack size attribute, so that applications receive the
137 full requested stack size, not diminished by the TCB and static TLS
138 allocation on the stack. Once the TCB is separately allocated,
139 this function should be removed or renamed (if it is still
140 necessary at that point). */
141 size_t
142 __pthread_get_minstack (const pthread_attr_t *attr)
143 {
144 return (GLRO(dl_pagesize) + __nptl_tls_static_size_for_stack ()
145 + PTHREAD_STACK_MIN);
146 }
147 libc_hidden_def (__pthread_get_minstack)