Bug #1202 » 0001-Fix-lttng-perf-counter-deadlock.patch
| liblttng-ust/lttng-context-perf-counters.c | ||
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#include <urcu/ref.h>
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#include <usterr-signal-safe.h>
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#include <signal.h>
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#include <urcu/tls-compat.h>
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#include "perf_event.h"
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#include "lttng-tracer-core.h"
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| ... | ... | |
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static pthread_key_t perf_counter_key;
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/*
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* lttng_perf_lock - Protect lttng-ust perf counter data structures
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*
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* Nests within the ust_lock, and therefore within the libc dl lock.
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* Therefore, we need to fixup the TLS before nesting into this lock.
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* Nests inside RCU bp read-side lock. Protects against concurrent
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* fork.
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*/
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static pthread_mutex_t ust_perf_mutex = PTHREAD_MUTEX_INITIALIZER;
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/*
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* Cancel state when grabbing the ust_perf_mutex. Saved when locking,
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* restored on unlock. Protected by ust_perf_mutex.
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*/
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static int ust_perf_saved_cancelstate;
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/*
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* Track whether we are tracing from a signal handler nested on an
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* application thread.
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*/
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static DEFINE_URCU_TLS(int, ust_perf_mutex_nest);
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/*
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* Force a read (imply TLS fixup for dlopen) of TLS variables.
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*/
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void lttng_ust_fixup_perf_counter_tls(void)
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{
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asm volatile ("" : : "m" (URCU_TLS(ust_perf_mutex_nest)));
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}
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void lttng_perf_lock(void)
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{
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sigset_t sig_all_blocked, orig_mask;
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int ret, oldstate;
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ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
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if (ret) {
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ERR("pthread_setcancelstate: %s", strerror(ret));
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}
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sigfillset(&sig_all_blocked);
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ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
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if (ret) {
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ERR("pthread_sigmask: %s", strerror(ret));
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}
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if (!URCU_TLS(ust_perf_mutex_nest)++) {
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/*
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* Ensure the compiler don't move the store after the close()
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* call in case close() would be marked as leaf.
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*/
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cmm_barrier();
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pthread_mutex_lock(&ust_perf_mutex);
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ust_perf_saved_cancelstate = oldstate;
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}
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ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
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if (ret) {
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ERR("pthread_sigmask: %s", strerror(ret));
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}
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}
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void lttng_perf_unlock(void)
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{
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sigset_t sig_all_blocked, orig_mask;
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int ret, newstate, oldstate;
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bool restore_cancel = false;
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sigfillset(&sig_all_blocked);
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ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
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if (ret) {
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ERR("pthread_sigmask: %s", strerror(ret));
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}
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/*
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* Ensure the compiler don't move the store before the close()
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* call, in case close() would be marked as leaf.
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*/
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cmm_barrier();
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if (!--URCU_TLS(ust_perf_mutex_nest)) {
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newstate = ust_perf_saved_cancelstate;
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restore_cancel = true;
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pthread_mutex_unlock(&ust_perf_mutex);
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}
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ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
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if (ret) {
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ERR("pthread_sigmask: %s", strerror(ret));
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}
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if (restore_cancel) {
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ret = pthread_setcancelstate(newstate, &oldstate);
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if (ret) {
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ERR("pthread_setcancelstate: %s", strerror(ret));
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}
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}
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}
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static
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size_t perf_counter_get_size(struct lttng_ctx_field *field, size_t offset)
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{
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| ... | ... | |
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* Note: thread_field->pc can be NULL if setup_perf() fails.
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* Also, thread_field->fd can be -1 if open_perf_fd() fails.
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*/
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ust_lock_nocheck();
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lttng_perf_lock();
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cds_list_add_rcu(&thread_field->rcu_field_node,
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&perf_thread->rcu_field_list);
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cds_list_add(&thread_field->thread_field_node,
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&perf_field->thread_field_list);
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ust_unlock();
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lttng_perf_unlock();
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skip:
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ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
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if (ret)
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| ... | ... | |
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value->u.s64 = wrapper_perf_counter_read(field);
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}
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/* Called with UST lock held */
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/* Called with perf lock held */
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static
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void lttng_destroy_perf_thread_field(
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struct lttng_perf_counter_thread_field *thread_field)
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| ... | ... | |
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struct lttng_perf_counter_thread *perf_thread = _key;
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struct lttng_perf_counter_thread_field *pos, *p;
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ust_lock_nocheck();
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lttng_perf_lock();
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cds_list_for_each_entry_safe(pos, p, &perf_thread->rcu_field_list,
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rcu_field_node)
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lttng_destroy_perf_thread_field(pos);
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ust_unlock();
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lttng_perf_unlock();
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free(perf_thread);
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}
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| ... | ... | |
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/*
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* This put is performed when no threads can concurrently
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* perform a "get" concurrently, thanks to urcu-bp grace
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* period.
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* period. Holding the lttng perf lock protects against
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* concurrent modification of the per-thread thread field
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* list.
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*/
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lttng_perf_lock();
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cds_list_for_each_entry_safe(pos, p, &perf_field->thread_field_list,
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thread_field_node)
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lttng_destroy_perf_thread_field(pos);
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lttng_perf_unlock();
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free(perf_field);
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}
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| liblttng-ust/lttng-tracer-core.h | ||
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int lttng_context_is_app(const char *name);
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void lttng_ust_fixup_tls(void);
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#ifdef LTTNG_UST_HAVE_PERF_EVENT
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void lttng_ust_fixup_perf_counter_tls(void);
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void lttng_perf_lock(void);
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void lttng_perf_unlock(void);
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#else /* #ifdef LTTNG_UST_HAVE_PERF_EVENT */
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static inline
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void lttng_ust_fixup_perf_counter_tls(void)
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{
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}
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static inline
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void lttng_perf_lock(void)
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{
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}
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static inline
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void lttng_perf_unlock(void)
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{
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}
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#endif /* #else #ifdef LTTNG_UST_HAVE_PERF_EVENT */
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#endif /* _LTTNG_TRACER_CORE_H */
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| liblttng-ust/lttng-ust-comm.c | ||
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lttng_fixup_nest_count_tls();
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lttng_fixup_procname_tls();
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lttng_fixup_ust_mutex_nest_tls();
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lttng_ust_fixup_perf_counter_tls();
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lttng_ust_fixup_fd_tracker_tls();
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}
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| ... | ... | |
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ust_lock_nocheck();
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urcu_bp_before_fork();
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lttng_ust_lock_fd_tracker();
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lttng_perf_lock();
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}
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static void ust_after_fork_common(sigset_t *restore_sigset)
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int ret;
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DBG("process %d", getpid());
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lttng_perf_unlock();
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lttng_ust_unlock_fd_tracker();
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ust_unlock();
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