[PATCH 06/10] perf/uprobe: Split uprobe_unregister()

[Peter Zijlstra]

With uprobe_unregister() having grown a synchronize_srcu(), it becomes
fairly slow to call. Esp. since both users of this API call it in a
loop.

Peel off the sync_srcu() and do it once, after the loop.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 include/linux/uprobes.h     |    8 ++++++--
 kernel/events/uprobes.c     |    8 ++++++--
 kernel/trace/bpf_trace.c    |    6 ++++--
 kernel/trace/trace_uprobe.c |    6 +++++-
 4 files changed, 21 insertions(+), 7 deletions(-)

--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -113,7 +113,8 @@ extern int uprobe_write_opcode(struct ar
 extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
 extern int uprobe_register_refctr(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc);
 extern int uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool);
-extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
+extern void uprobe_unregister_nosync(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
+extern void uprobe_unregister_sync(void);
 extern int uprobe_mmap(struct vm_area_struct *vma);
 extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
 extern void uprobe_start_dup_mmap(void);
@@ -163,7 +164,10 @@ uprobe_apply(struct inode *inode, loff_t
 	return -ENOSYS;
 }
 static inline void
-uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
+uprobe_unregister_nosync(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
+{
+}
+static inline void uprobes_unregister_sync(void)
 {
 }
 static inline int uprobe_mmap(struct vm_area_struct *vma)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1126,7 +1126,7 @@ __uprobe_unregister(struct uprobe *uprob
  * @offset: offset from the start of the file.
  * @uc: identify which probe if multiple probes are colocated.
  */
-void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
+void uprobe_unregister_nosync(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
 {
 	struct uprobe *uprobe;
 
@@ -1138,10 +1138,14 @@ void uprobe_unregister(struct inode *ino
 	__uprobe_unregister(uprobe, uc);
 	mutex_unlock(&uprobe->register_mutex);
 	put_uprobe(uprobe);
+}
+EXPORT_SYMBOL_GPL(uprobe_unregister_nosync);
 
+void uprobe_unregister_sync(void)
+{
 	synchronize_srcu(&uprobes_srcu);
 }
-EXPORT_SYMBOL_GPL(uprobe_unregister);
+EXPORT_SYMBOL_GPL(uprobe_unregister_sync);
 
 /*
  * __uprobe_register - register a probe
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3181,9 +3181,11 @@ static void bpf_uprobe_unregister(struct
 	u32 i;
 
 	for (i = 0; i < cnt; i++) {
-		uprobe_unregister(d_real_inode(path->dentry), uprobes[i].offset,
-				  &uprobes[i].consumer);
+		uprobe_unregister_nosync(d_real_inode(path->dentry), uprobes[i].offset,
+					 &uprobes[i].consumer);
 	}
+	if (cnt)
+		uprobe_unregister_sync();
 }
 
 static void bpf_uprobe_multi_link_release(struct bpf_link *link)
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -1104,6 +1104,7 @@ static int trace_uprobe_enable(struct tr
 static void __probe_event_disable(struct trace_probe *tp)
 {
 	struct trace_uprobe *tu;
+	bool sync = false;
 
 	tu = container_of(tp, struct trace_uprobe, tp);
 	WARN_ON(!uprobe_filter_is_empty(tu->tp.event->filter));
@@ -1112,9 +1113,12 @@ static void __probe_event_disable(struct
 		if (!tu->inode)
 			continue;
 
-		uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
+		uprobe_unregister_nosync(tu->inode, tu->offset, &tu->consumer);
+		sync = true;
 		tu->inode = NULL;
 	}
+	if (sync)
+		uprobe_unregister_sync();
 }
 
 static int probe_event_enable(struct trace_event_call *call,