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4d54fdee1d
For a generic explanation of why mutexs needed to be reimplemented to work with the kernel lock profiling see commits:e811949a57andd28db80fd0The specific changes made to the mutex implemetation are as follows. The Linux mutex structure is now directly embedded in the kmutex_t. This allows a kmutex_t to be directly case to a mutex struct and passed directly to the Linux primative. Just like with the rwlocks it is critical that these functions be implemented as '#defines to ensure the location information is preserved. The preprocessor can then do a direct replacement of the Solaris primative with the linux primative. Just as with the rwlocks we need to track the lock owner. Here things get a little more interesting because depending on your kernel version, and how you've built your kernel Linux may already do this for you. If your running a 2.6.29 or newer kernel on a SMP system the lock owner will be tracked. This was added to Linux to support adaptive mutexs, more on that shortly. Alternately, your kernel might track the lock owner if you've set CONFIG_DEBUG_MUTEXES in the kernel build. If neither of the above things is true for your kernel the kmutex_t type will include and track the lock owner to ensure correct behavior. This is all handled by a new autoconf check called SPL_AC_MUTEX_OWNER. Concerning adaptive mutexs these are a very recent development and they did not make it in to either the latest FC11 of SLES11 kernels. Ideally, I'd love to see this kernel change appear in one of these distros because it does help performance. From Linux kernel commit: 0d66bf6d3514b35eb6897629059443132992dbd7 "Testing with Ingo's test-mutex application... gave a 345% boost for VFS scalability on my testbox" However, if you don't want to backport this change yourself you can still simply export the task_curr() symbol. The kmutex_t implementation will use this symbol when it's available to provide it's own adaptive mutexs. Finally, DEBUG_MUTEX support was removed including the proc handlers. This was done because now that we are cleanly integrated with the kernel profiling all this information and much much more is available in debug kernel builds. This code was now redundant. Update mutexs validated on: - SLES10 (ppc64) - SLES11 (x86_64) - CHAOS4.2 (x86_64) - RHEL5.3 (x86_64) - RHEL6 (x86_64) - FC11 (x86_64)
202 lines
7.6 KiB
C
202 lines
7.6 KiB
C
/*
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* This file is part of the SPL: Solaris Porting Layer.
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*
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* Copyright (c) 2009 Lawrence Livermore National Security, LLC.
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* Produced at Lawrence Livermore National Laboratory
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* Written by:
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* Brian Behlendorf <behlendorf1@llnl.gov>,
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* Herb Wartens <wartens2@llnl.gov>,
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* Jim Garlick <garlick@llnl.gov>
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* UCRL-CODE-235197
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*
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* This is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef _SPL_MUTEX_H
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#define _SPL_MUTEX_H
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#include <sys/types.h>
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#include <linux/mutex.h>
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typedef enum {
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MUTEX_DEFAULT = 0,
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MUTEX_SPIN = 1,
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MUTEX_ADAPTIVE = 2
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} kmutex_type_t;
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#ifdef HAVE_MUTEX_OWNER
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typedef struct mutex kmutex_t;
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static inline kthread_t *
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mutex_owner(kmutex_t *mp)
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{
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if (mp->owner)
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return (mp->owner)->task;
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return NULL;
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}
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#define mutex_owned(mp) (mutex_owner(mp) == current)
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#define MUTEX_HELD(mp) mutex_owned(mp)
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#undef mutex_init
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#define mutex_init(mp, name, type, ibc) \
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({ \
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static struct lock_class_key __key; \
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ASSERT(type == MUTEX_DEFAULT); \
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\
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__mutex_init((mp), #mp, &__key); \
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})
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/* #define mutex_destroy(mp) ((void)0) */
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#define mutex_tryenter(mp) mutex_trylock(mp)
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#define mutex_enter(mp) mutex_lock(mp)
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#define mutex_exit(mp) mutex_unlock(mp)
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#else /* HAVE_MUTEX_OWNER */
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typedef struct {
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struct mutex m_mutex;
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kthread_t *m_owner;
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} kmutex_t;
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#ifdef HAVE_TASK_CURR
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extern int spl_mutex_spin_max(void);
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#else /* HAVE_TASK_CURR */
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# define task_curr(owner) 0
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# define spl_mutex_spin_max() 0
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#endif /* HAVE_TASK_CURR */
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#define MUTEX(mp) ((struct mutex *)(mp))
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static inline kthread_t *
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spl_mutex_get_owner(kmutex_t *mp)
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{
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return mp->m_owner;
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}
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static inline void
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spl_mutex_set_owner(kmutex_t *mp)
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{
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unsigned long flags;
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spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
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mp->m_owner = current;
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spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
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}
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static inline void
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spl_mutex_clear_owner(kmutex_t *mp)
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{
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unsigned long flags;
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spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
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mp->m_owner = NULL;
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spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
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}
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static inline kthread_t *
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mutex_owner(kmutex_t *mp)
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{
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unsigned long flags;
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kthread_t *owner;
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spin_lock_irqsave(&MUTEX(mp)->wait_lock, flags);
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owner = spl_mutex_get_owner(mp);
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spin_unlock_irqrestore(&MUTEX(mp)->wait_lock, flags);
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return owner;
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}
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#define mutex_owned(mp) (mutex_owner(mp) == current)
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#define MUTEX_HELD(mp) mutex_owned(mp)
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/*
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* The following functions must be a #define and not static inline.
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* This ensures that the native linux mutex functions (lock/unlock)
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* will be correctly located in the users code which is important
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* for the built in kernel lock analysis tools
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*/
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#undef mutex_init
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#define mutex_init(mp, name, type, ibc) \
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({ \
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static struct lock_class_key __key; \
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ASSERT(type == MUTEX_DEFAULT); \
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\
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__mutex_init(MUTEX(mp), #mp, &__key); \
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spl_mutex_clear_owner(mp); \
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})
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#undef mutex_destroy
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#define mutex_destroy(mp) \
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({ \
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VERIFY(!MUTEX_HELD(mp)); \
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})
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#define mutex_tryenter(mp) \
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({ \
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int _rc_; \
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\
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if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) \
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spl_mutex_set_owner(mp); \
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\
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_rc_; \
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})
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/*
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* Adaptive mutexs assume that the lock may be held by a task running
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* on a different cpu. The expectation is that the task will drop the
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* lock before leaving the head of the run queue. So the ideal thing
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* to do is spin until we acquire the lock and avoid a context switch.
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* However it is also possible the task holding the lock yields the
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* processor with out dropping lock. In this case, we know it's going
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* to be a while so we stop spinning and go to sleep waiting for the
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* lock to be available. This should strike the optimum balance
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* between spinning and sleeping waiting for a lock.
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*/
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#define mutex_enter(mp) \
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({ \
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kthread_t *_owner_; \
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int _rc_, _count_; \
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\
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_rc_ = 0; \
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_count_ = 0; \
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_owner_ = mutex_owner(mp); \
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\
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while (_owner_ && task_curr(_owner_) && \
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_count_ <= spl_mutex_spin_max()) { \
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if ((_rc_ = mutex_trylock(MUTEX(mp)))) \
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break; \
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\
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_count_++; \
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} \
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\
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if (!_rc_) \
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mutex_lock(MUTEX(mp)); \
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\
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spl_mutex_set_owner(mp); \
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})
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#define mutex_exit(mp) \
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({ \
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spl_mutex_clear_owner(mp); \
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mutex_unlock(MUTEX(mp)); \
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})
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#endif /* HAVE_MUTEX_OWNER */
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int spl_mutex_init(void);
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void spl_mutex_fini(void);
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#endif /* _SPL_MUTEX_H */
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