On Thu, Jul 30, 2026 at 10:45:39AM +0900, Masami Hiramatsu (Google) wrote: > From: Masami Hiramatsu (Google) <[email protected]> > > find_active_uprobe_speculative() is called from find_active_uprobe_rcu(), > which is invoked by handle_swbp() and handle_syscall_uprobe(). > Both callers already hold RCU Tasks Trace (via rcu_read_lock_trace() or > guard(rcu_tasks_trace)()). > > Calling guard(rcu)() inside find_active_uprobe_speculative() is redundant > because the caller already guarantees RCU Tasks Trace protection. > Furthermore, standard RCU (rcu_read_lock()) does not protect uprobes_tree > against asynchronous uprobe destruction (call_rcu_tasks_trace()). > > Remove the redundant guard(rcu)() from find_active_uprobe_speculative() and > replace it with lockdep_assert(rcu_read_lock_trace_held()) and a comment > documenting that callers must hold RCU Tasks Trace protection, matching the > convention used by find_active_uprobe_rcu() and find_uprobe_rcu(). > > Fixes: e0925f2dc4de ("uprobes: add speculative lockless > VMA-to-inode-to-uprobe resolution") > Assisted-by: Antigravity:gemini-3.6-flash > Signed-off-by: Masami Hiramatsu (Google) <[email protected]> > --- > kernel/events/uprobes.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index 4084e926e284..b4e253d43b30 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -2424,6 +2424,7 @@ static int is_trap_at_addr(struct mm_struct *mm, > unsigned long vaddr) > return is_trap_insn(&opcode); > } > > +/* assumes being inside RCU Tasks Trace protected region */ > static struct uprobe *find_active_uprobe_speculative(unsigned long bp_vaddr) > { > struct mm_struct *mm = current->mm; > @@ -2433,7 +2434,7 @@ static struct uprobe > *find_active_uprobe_speculative(unsigned long bp_vaddr) > loff_t offset; > unsigned int seq; > > - guard(rcu)(); > + lockdep_assert(rcu_read_lock_trace_held()); > > if (!mmap_lock_speculate_try_begin(mm, &seq)) > return NULL;
Seems fine, but it this really worthy of Fixes? I mean, its just a micro optimization, no?
