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authorOleg Nesterov <oleg@redhat.com>2012-11-24 17:29:40 +0100
committerOleg Nesterov <oleg@redhat.com>2013-02-08 17:47:03 +0100
commite591c8d78e49e6206935cf31c4d2b603bbb29166 (patch)
treefd454634604829933828e06849550dfbcfc37542 /kernel/events
parent9a98e03cc145c994da824dac7602334f50feb670 (diff)
downloadop-kernel-dev-e591c8d78e49e6206935cf31c4d2b603bbb29166.zip
op-kernel-dev-e591c8d78e49e6206935cf31c4d2b603bbb29166.tar.gz
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.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index d1d1394..61d0fa6 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);
}
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