diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2012-11-24 17:29:40 +0100 |
|---|---|---|
| committer | Oleg Nesterov <oleg@redhat.com> | 2013-02-08 17:47:03 +0100 |
| commit | e591c8d78e49e6206935cf31c4d2b603bbb29166 (patch) | |
| tree | fd454634604829933828e06849550dfbcfc37542 /kernel/events | |
| parent | 9a98e03cc145c994da824dac7602334f50feb670 (diff) | |
uprobes: Introduce uprobe->register_rwsem
Introduce uprobe->register_rwsem. It is taken for writing around
__uprobe_register/unregister.
Change handler_chain() to use this sem rather than consumer_rwsem.
The main reason for this change is that we have the nasty problem
with mmap_sem/consumer_rwsem dependency. filter_chain() needs to
protect uprobe->consumers like handler_chain(), but they can not
use the same lock. filter_chain() can be called under ->mmap_sem
(currently this is always true), but we want to allow ->handler()
to play with the probed task's memory, and this needs ->mmap_sem.
Alternatively we could use srcu, but synchronize_srcu() is very
slow and ->register_rwsem allows us to do more. In particular, we
can teach handler_chain() to do remove_breakpoint() if this bp is
"nacked" by all consumers, we know that we can't race with the
new consumer which does uprobe_register().
See also the next patches. uprobes_mutex[] is almost ready to die.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/uprobes.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index d1d1394bca8b..61d0fa6b5012 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -91,6 +91,7 @@ static atomic_t uprobe_events = ATOMIC_INIT(0); struct uprobe { struct rb_node rb_node; /* node in the rb tree */ atomic_t ref; + struct rw_semaphore register_rwsem; struct rw_semaphore consumer_rwsem; struct mutex copy_mutex; /* TODO: kill me and UPROBE_COPY_INSN */ struct list_head pending_list; @@ -449,6 +450,7 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset) uprobe->inode = igrab(inode); uprobe->offset = offset; + init_rwsem(&uprobe->register_rwsem); init_rwsem(&uprobe->consumer_rwsem); mutex_init(&uprobe->copy_mutex); /* For now assume that the instruction need not be single-stepped */ @@ -476,10 +478,10 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) if (!test_bit(UPROBE_RUN_HANDLER, &uprobe->flags)) return; - down_read(&uprobe->consumer_rwsem); + down_read(&uprobe->register_rwsem); for (uc = uprobe->consumers; uc; uc = uc->next) uc->handler(uc, regs); - up_read(&uprobe->consumer_rwsem); + up_read(&uprobe->register_rwsem); } static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc) @@ -873,9 +875,11 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer * mutex_lock(uprobes_hash(inode)); uprobe = alloc_uprobe(inode, offset); if (uprobe) { + down_write(&uprobe->register_rwsem); ret = __uprobe_register(uprobe, uc); if (ret) __uprobe_unregister(uprobe, uc); + up_write(&uprobe->register_rwsem); } mutex_unlock(uprobes_hash(inode)); if (uprobe) @@ -899,7 +903,9 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume return; mutex_lock(uprobes_hash(inode)); + down_write(&uprobe->register_rwsem); __uprobe_unregister(uprobe, uc); + up_write(&uprobe->register_rwsem); mutex_unlock(uprobes_hash(inode)); put_uprobe(uprobe); } |