Now that we have a good separate of each registration step, take uprobes_treelock just once for relevant registration step, and then process all relevant uprobes in one go. Even if writer lock introduces a relatively large delay (as might happen with per-CPU RW semaphore), this will keep overall batch attachment reasonably fast. We teach put_uprobe(), though __put_uprobe() helper, to optionally take or not uprobes_treelock, to accommodate this pattern. With these changes we don't need insert_uprobe() operation that unconditionally takes uprobes_treelock, so get rid of it, leaving only lower-level __insert_uprobe() helper. Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> --- kernel/events/uprobes.c | 45 +++++++++++++++++++++-------------------- 1 file changed, 23 insertions(+), 22 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 5e98e179d47d..416f408cbed9 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -657,7 +657,7 @@ static inline bool uprobe_is_active(struct uprobe *uprobe) return !RB_EMPTY_NODE(&uprobe->rb_node); } -static void put_uprobe(struct uprobe *uprobe) +static void __put_uprobe(struct uprobe *uprobe, bool tree_locked) { s64 v; @@ -666,7 +666,8 @@ static void put_uprobe(struct uprobe *uprobe) if (unlikely((u32)v == 0)) { bool destroy; - write_lock(&uprobes_treelock); + if (!tree_locked) + write_lock(&uprobes_treelock); /* * We might race with find_uprobe()->__get_uprobe() executed * from inside read-locked uprobes_treelock, which can bump @@ -689,7 +690,8 @@ static void put_uprobe(struct uprobe *uprobe) destroy = atomic64_read(&uprobe->ref) == v; if (destroy && uprobe_is_active(uprobe)) rb_erase(&uprobe->rb_node, &uprobes_tree); - write_unlock(&uprobes_treelock); + if (!tree_locked) + write_unlock(&uprobes_treelock); /* uprobe got resurrected, pretend we never tried to free it */ if (!destroy) @@ -718,6 +720,11 @@ static void put_uprobe(struct uprobe *uprobe) (void)atomic64_cmpxchg(&uprobe->ref, v, v & ~(1ULL << 63)); } +static void put_uprobe(struct uprobe *uprobe) +{ + __put_uprobe(uprobe, false); +} + static __always_inline int uprobe_cmp(const struct inode *l_inode, const loff_t l_offset, const struct uprobe *r) @@ -817,21 +824,6 @@ static struct uprobe *__insert_uprobe(struct uprobe *uprobe) return u; } -/* - * Acquire uprobes_treelock and insert uprobe into uprobes_tree - * (or reuse existing one, see __insert_uprobe() comments above). - */ -static struct uprobe *insert_uprobe(struct uprobe *uprobe) -{ - struct uprobe *u; - - write_lock(&uprobes_treelock); - u = __insert_uprobe(uprobe); - write_unlock(&uprobes_treelock); - - return u; -} - static void ref_ctr_mismatch_warn(struct uprobe *cur_uprobe, struct uprobe *uprobe) { @@ -1291,6 +1283,8 @@ int uprobe_register_batch(struct inode *inode, int cnt, uc->uprobe = uprobe; } + ret = 0; + write_lock(&uprobes_treelock); for (i = 0; i < cnt; i++) { struct uprobe *cur_uprobe; @@ -1298,19 +1292,24 @@ int uprobe_register_batch(struct inode *inode, int cnt, uprobe = uc->uprobe; /* add to uprobes_tree, sorted on inode:offset */ - cur_uprobe = insert_uprobe(uprobe); + cur_uprobe = __insert_uprobe(uprobe); /* a uprobe exists for this inode:offset combination */ if (cur_uprobe != uprobe) { if (cur_uprobe->ref_ctr_offset != uprobe->ref_ctr_offset) { ref_ctr_mismatch_warn(cur_uprobe, uprobe); - put_uprobe(cur_uprobe); + + __put_uprobe(cur_uprobe, true); ret = -EINVAL; - goto cleanup_uprobes; + goto unlock_treelock; } kfree(uprobe); uc->uprobe = cur_uprobe; } } +unlock_treelock: + write_unlock(&uprobes_treelock); + if (ret) + goto cleanup_uprobes; for (i = 0; i < cnt; i++) { uc = get_uprobe_consumer(i, ctx); @@ -1340,12 +1339,14 @@ int uprobe_register_batch(struct inode *inode, int cnt, } cleanup_uprobes: /* put all the successfully allocated/reused uprobes */ + write_lock(&uprobes_treelock); for (i = cnt - 1; i >= 0; i--) { uc = get_uprobe_consumer(i, ctx); - put_uprobe(uc->uprobe); + __put_uprobe(uc->uprobe, true); uc->uprobe = NULL; } + write_unlock(&uprobes_treelock); return ret; } -- 2.43.0