Re: [PATCH v2 07/11] perf/uprobe: Split uprobe_unregister()

Andrii Nakryiko
2024-07-12T21:10:46Z

+ bpf

On Thu, Jul 11, 2024 at 4:07 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> 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@infradead.org>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> ---
> 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(-)
>

BPF side of things looks good:

Acked-by: Andrii Nakryiko <andrii@kernel.org>

> --- 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
> @@ -1138,7 +1138,7 @@ __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;
>
> @@ -1152,10 +1152,14 @@ void uprobe_unregister(struct inode *ino
> raw_write_seqcount_end(&uprobe->register_seq);
> up_write(&uprobe->register_rwsem);
> 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,
>
>