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
23size_t __nptl_stack_cache_maxsize = 40 * 1024 * 1024;
24
25void
26__nptl_stack_list_del (list_t *elem)
27{
28 GL (dl_in_flight_stack) = (uintptr_t) elem;
29
30 atomic_write_barrier ();
31
32 list_del (elem);
33
34 atomic_write_barrier ();
35
36 GL (dl_in_flight_stack) = 0;
37}
38libc_hidden_def (__nptl_stack_list_del)
39
40void
41__nptl_stack_list_add (list_t *elem, list_t *list)
42{
43 GL (dl_in_flight_stack) = (uintptr_t) elem | 1;
44
45 atomic_write_barrier ();
46
47 list_add (elem, list);
48
49 atomic_write_barrier ();
50
51 GL (dl_in_flight_stack) = 0;
52}
53libc_hidden_def (__nptl_stack_list_add)
54
55void
56__nptl_free_stacks (size_t limit)
57{
58 /* We reduce the size of the cache. Remove the last entries until
59 the size is below the limit. */
60 list_t *entry;
61 list_t *prev;
62
63 /* Search from the end of the list. */
64 list_for_each_prev_safe (entry, prev, &GL (dl_stack_cache))
65 {
66 struct pthread *curr;
67
68 curr = list_entry (entry, struct pthread, list);
69 if (__nptl_stack_in_use (curr))
70 {
71 /* Unlink the block. */
72 __nptl_stack_list_del (entry);
73
74 /* Account for the freed memory. */
75 GL (dl_stack_cache_actsize) -= curr->stackblock_size;
76
77 /* Free the memory associated with the ELF TLS. */
78 _dl_deallocate_tls (TLS_TPADJ (curr), false);
79
80 /* Remove this block. This should never fail. If it does
81 something is really wrong. */
82 if (__munmap (curr->stackblock, curr->stackblock_size) != 0)
83 abort ();
84
85 /* Maybe we have freed enough. */
86 if (GL (dl_stack_cache_actsize) <= limit)
87 break;
88 }
89 }
90}
91
92/* Add a stack frame which is not used anymore to the stack. Must be
93 called with the cache lock held. */
94static inline void
95__attribute ((always_inline))
96queue_stack (struct pthread *stack)
97{
98 /* We unconditionally add the stack to the list. The memory may
99 still be in use but it will not be reused until the kernel marks
100 the stack as not used anymore. */
101 __nptl_stack_list_add (&stack->list, &GL (dl_stack_cache));
102
103 GL (dl_stack_cache_actsize) += stack->stackblock_size;
104 if (__glibc_unlikely (GL (dl_stack_cache_actsize)
105 > __nptl_stack_cache_maxsize))
106 __nptl_free_stacks (__nptl_stack_cache_maxsize);
107}
108
109void
110__nptl_deallocate_stack (struct pthread *pd)
111{
112 lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
113
114 /* Remove the thread from the list of threads with user defined
115 stacks. */
116 __nptl_stack_list_del (&pd->list);
117
118 /* Not much to do. Just free the mmap()ed memory. Note that we do
119 not reset the 'used' flag in the 'tid' field. This is done by
120 the kernel. If no thread has been created yet this field is
121 still zero. */
122 if (__glibc_likely (! pd->user_stack))
123 (void) queue_stack (pd);
124 else
125 /* Free the memory associated with the ELF TLS. */
126 _dl_deallocate_tls (TLS_TPADJ (pd), false);
127
128 lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
129}
130libc_hidden_def (__nptl_deallocate_stack)
131
132/* This function is internal (it has a GLIBC_PRIVATE) version, but it
133 is widely used (either via weak symbol, or dlsym) to obtain the
134 __static_tls_size value. This value is then used to adjust the
135 value of the stack size attribute, so that applications receive the
136 full requested stack size, not diminished by the TCB and static TLS
137 allocation on the stack. Once the TCB is separately allocated,
138 this function should be removed or renamed (if it is still
139 necessary at that point). */
140size_t
141__pthread_get_minstack (const pthread_attr_t *attr)
142{
143 return (GLRO(dl_pagesize) + __nptl_tls_static_size_for_stack ()
144 + PTHREAD_STACK_MIN);
145}
146libc_hidden_def (__pthread_get_minstack)
147