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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2022-02-17 11:23:59 +0100
committerThomas Gleixner <tglx@linutronix.de>2022-02-22 22:25:01 +0100
commitbe9a2277cafd318976d59c41a7f45a934ec43b26 (patch)
tree66165b83a6a06c0ef82f201486fc0db20b82742b /kernel/fork.c
parentcfb92440ee71adcc2105b0890bb01ac3cddb8507 (diff)
fork: Redo ifdefs around task stack handling
The use of ifdef CONFIG_VMAP_STACK is confusing in terms what is actually happenning and what can happen. For instance from reading free_thread_stack() it appears that in the CONFIG_VMAP_STACK case it may receive a non-NULL vm pointer but it may also be NULL in which case __free_pages() is used to free the stack. This is however not the case because in the VMAP case a non-NULL pointer is always returned here. Since it looks like this might happen, the compiler creates the correct dead code with the invocation to __free_pages() and everything around it. Twice. Add spaces between the ifdef and the identifer to recognize the ifdef level which is currently in scope. Add the current identifer as a comment behind #else and #endif. Move the code within free_thread_stack() and alloc_thread_stack_node() into the relevant ifdef blocks. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Andy Lutomirski <luto@kernel.org> Link: https://lore.kernel.org/r/20220217102406.3697941-2-bigeasy@linutronix.de
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c74
1 files changed, 39 insertions, 35 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index a024bf6254df..f5cc10164334 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -185,7 +185,7 @@ static inline void free_task_struct(struct task_struct *tsk)
*/
# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
-#ifdef CONFIG_VMAP_STACK
+# ifdef CONFIG_VMAP_STACK
/*
* vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
* flush. Try to minimize the number of calls by caching stacks.
@@ -210,11 +210,9 @@ static int free_vm_stack_cache(unsigned int cpu)
return 0;
}
-#endif
static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
{
-#ifdef CONFIG_VMAP_STACK
void *stack;
int i;
@@ -258,45 +256,53 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
tsk->stack = stack;
}
return stack;
-#else
- struct page *page = alloc_pages_node(node, THREADINFO_GFP,
- THREAD_SIZE_ORDER);
-
- if (likely(page)) {
- tsk->stack = kasan_reset_tag(page_address(page));
- return tsk->stack;
- }
- return NULL;
-#endif
}
-static inline void free_thread_stack(struct task_struct *tsk)
+static void free_thread_stack(struct task_struct *tsk)
{
-#ifdef CONFIG_VMAP_STACK
struct vm_struct *vm = task_stack_vm_area(tsk);
+ int i;
- if (vm) {
- int i;
+ for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
+ memcg_kmem_uncharge_page(vm->pages[i], 0);
- for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
- memcg_kmem_uncharge_page(vm->pages[i], 0);
+ for (i = 0; i < NR_CACHED_STACKS; i++) {
+ if (this_cpu_cmpxchg(cached_stacks[i], NULL,
+ tsk->stack_vm_area) != NULL)
+ continue;
- for (i = 0; i < NR_CACHED_STACKS; i++) {
- if (this_cpu_cmpxchg(cached_stacks[i],
- NULL, tsk->stack_vm_area) != NULL)
- continue;
+ tsk->stack = NULL;
+ tsk->stack_vm_area = NULL;
+ return;
+ }
+ vfree_atomic(tsk->stack);
+ tsk->stack = NULL;
+ tsk->stack_vm_area = NULL;
+}
- return;
- }
+# else /* !CONFIG_VMAP_STACK */
- vfree_atomic(tsk->stack);
- return;
+static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
+{
+ struct page *page = alloc_pages_node(node, THREADINFO_GFP,
+ THREAD_SIZE_ORDER);
+
+ if (likely(page)) {
+ tsk->stack = kasan_reset_tag(page_address(page));
+ return tsk->stack;
}
-#endif
+ return NULL;
+}
+static void free_thread_stack(struct task_struct *tsk)
+{
__free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER);
+ tsk->stack = NULL;
}
-# else
+
+# endif /* CONFIG_VMAP_STACK */
+# else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */
+
static struct kmem_cache *thread_stack_cache;
static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
@@ -312,6 +318,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
static void free_thread_stack(struct task_struct *tsk)
{
kmem_cache_free(thread_stack_cache, tsk->stack);
+ tsk->stack = NULL;
}
void thread_stack_cache_init(void)
@@ -321,8 +328,9 @@ void thread_stack_cache_init(void)
THREAD_SIZE, NULL);
BUG_ON(thread_stack_cache == NULL);
}
-# endif
-#endif
+
+# endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
+#endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
/* SLAB cache for signal_struct structures (tsk->signal) */
static struct kmem_cache *signal_cachep;
@@ -432,10 +440,6 @@ static void release_task_stack(struct task_struct *tsk)
account_kernel_stack(tsk, -1);
free_thread_stack(tsk);
- tsk->stack = NULL;
-#ifdef CONFIG_VMAP_STACK
- tsk->stack_vm_area = NULL;
-#endif
}
#ifdef CONFIG_THREAD_INFO_IN_TASK