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The swevent_htable::recursion counter is used to avoid creating an swevent while an event is processed to avoid recursion. The counter is per-CPU and preemption must be disabled to have a stable counter. perf_pending_task() disables preemption to access the counter and then signal. This is problematic on PREEMPT_RT because sending a signal uses a spinlock_t which must not be acquired in atomic on PREEMPT_RT because it becomes a sleeping lock. The atomic context can be avoided by moving the counter into the task_struct. There is a 4 byte hole between futex_state (usually always on) and the following perf pointer (perf_event_ctxp). After the recursion lost some weight it fits perfectly. Move swevent_htable::recursion into task_struct. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Marco Elver <elver@google.com> Link: https://lore.kernel.org/r/20240704170424.1466941-6-bigeasy@linutronix.de
247 lines
5.8 KiB
C
247 lines
5.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _KERNEL_EVENTS_INTERNAL_H
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#define _KERNEL_EVENTS_INTERNAL_H
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#include <linux/hardirq.h>
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#include <linux/uaccess.h>
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#include <linux/refcount.h>
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/* Buffer handling */
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#define RING_BUFFER_WRITABLE 0x01
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struct perf_buffer {
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refcount_t refcount;
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struct rcu_head rcu_head;
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#ifdef CONFIG_PERF_USE_VMALLOC
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struct work_struct work;
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int page_order; /* allocation order */
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#endif
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int nr_pages; /* nr of data pages */
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int overwrite; /* can overwrite itself */
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int paused; /* can write into ring buffer */
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atomic_t poll; /* POLL_ for wakeups */
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local_t head; /* write position */
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unsigned int nest; /* nested writers */
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local_t events; /* event limit */
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local_t wakeup; /* wakeup stamp */
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local_t lost; /* nr records lost */
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long watermark; /* wakeup watermark */
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long aux_watermark;
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/* poll crap */
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spinlock_t event_lock;
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struct list_head event_list;
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atomic_t mmap_count;
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unsigned long mmap_locked;
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struct user_struct *mmap_user;
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/* AUX area */
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long aux_head;
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unsigned int aux_nest;
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long aux_wakeup; /* last aux_watermark boundary crossed by aux_head */
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unsigned long aux_pgoff;
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int aux_nr_pages;
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int aux_overwrite;
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atomic_t aux_mmap_count;
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unsigned long aux_mmap_locked;
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void (*free_aux)(void *);
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refcount_t aux_refcount;
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int aux_in_sampling;
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void **aux_pages;
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void *aux_priv;
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struct perf_event_mmap_page *user_page;
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void *data_pages[];
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};
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extern void rb_free(struct perf_buffer *rb);
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static inline void rb_free_rcu(struct rcu_head *rcu_head)
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{
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struct perf_buffer *rb;
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rb = container_of(rcu_head, struct perf_buffer, rcu_head);
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rb_free(rb);
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}
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static inline void rb_toggle_paused(struct perf_buffer *rb, bool pause)
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{
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if (!pause && rb->nr_pages)
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rb->paused = 0;
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else
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rb->paused = 1;
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}
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extern struct perf_buffer *
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rb_alloc(int nr_pages, long watermark, int cpu, int flags);
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extern void perf_event_wakeup(struct perf_event *event);
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extern int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event,
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pgoff_t pgoff, int nr_pages, long watermark, int flags);
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extern void rb_free_aux(struct perf_buffer *rb);
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extern struct perf_buffer *ring_buffer_get(struct perf_event *event);
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extern void ring_buffer_put(struct perf_buffer *rb);
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static inline bool rb_has_aux(struct perf_buffer *rb)
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{
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return !!rb->aux_nr_pages;
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}
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void perf_event_aux_event(struct perf_event *event, unsigned long head,
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unsigned long size, u64 flags);
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extern struct page *
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perf_mmap_to_page(struct perf_buffer *rb, unsigned long pgoff);
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#ifdef CONFIG_PERF_USE_VMALLOC
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/*
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* Back perf_mmap() with vmalloc memory.
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*
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* Required for architectures that have d-cache aliasing issues.
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*/
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static inline int page_order(struct perf_buffer *rb)
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{
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return rb->page_order;
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}
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#else
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static inline int page_order(struct perf_buffer *rb)
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{
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return 0;
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}
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#endif
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static inline int data_page_nr(struct perf_buffer *rb)
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{
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return rb->nr_pages << page_order(rb);
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}
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static inline unsigned long perf_data_size(struct perf_buffer *rb)
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{
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return rb->nr_pages << (PAGE_SHIFT + page_order(rb));
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}
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static inline unsigned long perf_aux_size(struct perf_buffer *rb)
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{
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return (unsigned long)rb->aux_nr_pages << PAGE_SHIFT;
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}
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#define __DEFINE_OUTPUT_COPY_BODY(advance_buf, memcpy_func, ...) \
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{ \
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unsigned long size, written; \
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\
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do { \
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size = min(handle->size, len); \
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written = memcpy_func(__VA_ARGS__); \
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written = size - written; \
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\
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len -= written; \
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handle->addr += written; \
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if (advance_buf) \
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buf += written; \
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handle->size -= written; \
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if (!handle->size) { \
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struct perf_buffer *rb = handle->rb; \
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\
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handle->page++; \
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handle->page &= rb->nr_pages - 1; \
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handle->addr = rb->data_pages[handle->page]; \
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handle->size = PAGE_SIZE << page_order(rb); \
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} \
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} while (len && written == size); \
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\
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return len; \
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}
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#define DEFINE_OUTPUT_COPY(func_name, memcpy_func) \
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static inline unsigned long \
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func_name(struct perf_output_handle *handle, \
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const void *buf, unsigned long len) \
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__DEFINE_OUTPUT_COPY_BODY(true, memcpy_func, handle->addr, buf, size)
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static inline unsigned long
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__output_custom(struct perf_output_handle *handle, perf_copy_f copy_func,
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const void *buf, unsigned long len)
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{
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unsigned long orig_len = len;
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__DEFINE_OUTPUT_COPY_BODY(false, copy_func, handle->addr, buf,
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orig_len - len, size)
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}
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static inline unsigned long
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memcpy_common(void *dst, const void *src, unsigned long n)
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{
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memcpy(dst, src, n);
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return 0;
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}
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DEFINE_OUTPUT_COPY(__output_copy, memcpy_common)
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static inline unsigned long
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memcpy_skip(void *dst, const void *src, unsigned long n)
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{
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return 0;
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}
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DEFINE_OUTPUT_COPY(__output_skip, memcpy_skip)
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#ifndef arch_perf_out_copy_user
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#define arch_perf_out_copy_user arch_perf_out_copy_user
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static inline unsigned long
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arch_perf_out_copy_user(void *dst, const void *src, unsigned long n)
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{
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unsigned long ret;
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pagefault_disable();
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ret = __copy_from_user_inatomic(dst, src, n);
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pagefault_enable();
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return ret;
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}
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#endif
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DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user)
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static inline int get_recursion_context(u8 *recursion)
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{
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unsigned char rctx = interrupt_context_level();
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if (recursion[rctx])
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return -1;
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recursion[rctx]++;
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barrier();
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return rctx;
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}
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static inline void put_recursion_context(u8 *recursion, unsigned char rctx)
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{
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barrier();
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recursion[rctx]--;
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}
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#ifdef CONFIG_HAVE_PERF_USER_STACK_DUMP
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static inline bool arch_perf_have_user_stack_dump(void)
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{
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return true;
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}
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#define perf_user_stack_pointer(regs) user_stack_pointer(regs)
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#else
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static inline bool arch_perf_have_user_stack_dump(void)
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{
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return false;
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}
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#define perf_user_stack_pointer(regs) 0
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#endif /* CONFIG_HAVE_PERF_USER_STACK_DUMP */
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#endif /* _KERNEL_EVENTS_INTERNAL_H */
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