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8ebe34731a
Add lockdep annotations. Not only this can help to find the potential problems, we do not want the false warnings if, say, the task takes two different percpu_rw_semaphore's for reading. IOW, at least ->rw_sem should not use a single class. This patch exposes this internal lock to lockdep so that it represents the whole percpu_rw_semaphore. This way we do not need to add another "fake" ->lockdep_map and lock_class_key. More importantly, this also makes the output from lockdep much more understandable if it finds the problem. In short, with this patch from lockdep pov percpu_down_read() and percpu_up_read() acquire/release ->rw_sem for reading, this matches the actual semantics. This abuses __up_read() but I hope this is fine and in fact I'd like to have down_read_no_lockdep() as well, percpu_down_read_recursive_readers() will need it. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Anton Arapov <anton@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
35 lines
927 B
C
35 lines
927 B
C
#ifndef _LINUX_PERCPU_RWSEM_H
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#define _LINUX_PERCPU_RWSEM_H
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#include <linux/atomic.h>
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#include <linux/rwsem.h>
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#include <linux/percpu.h>
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#include <linux/wait.h>
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#include <linux/lockdep.h>
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struct percpu_rw_semaphore {
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unsigned int __percpu *fast_read_ctr;
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atomic_t write_ctr;
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struct rw_semaphore rw_sem;
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atomic_t slow_read_ctr;
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wait_queue_head_t write_waitq;
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};
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extern void percpu_down_read(struct percpu_rw_semaphore *);
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extern void percpu_up_read(struct percpu_rw_semaphore *);
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extern void percpu_down_write(struct percpu_rw_semaphore *);
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extern void percpu_up_write(struct percpu_rw_semaphore *);
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extern int __percpu_init_rwsem(struct percpu_rw_semaphore *,
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const char *, struct lock_class_key *);
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extern void percpu_free_rwsem(struct percpu_rw_semaphore *);
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#define percpu_init_rwsem(brw) \
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({ \
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static struct lock_class_key rwsem_key; \
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__percpu_init_rwsem(brw, #brw, &rwsem_key); \
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})
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#endif
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