[PATCH v2 05/11] perf/uprobe: Simplify UPROBE_HANDLER_REMOVE logic
From: Peter Zijlstra <peterz@infradead.org>
Date: 2024-07-11 11:07:27
Also in:
lkml
Specifically, get rid of the uprobe->consumers re-load, which isn't sound under RCU. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/events/uprobes.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c@@ -2101,6 +2101,7 @@ static void handler_chain(struct uprobe struct uprobe_consumer *uc; int remove = UPROBE_HANDLER_REMOVE; bool need_prep = false; /* prepare return uprobe, when needed */ + bool had_handler = false; down_read(&uprobe->register_rwsem); for (uc = uprobe->consumers; uc; uc = uc->next) {
@@ -2115,16 +2116,26 @@ static void handler_chain(struct uprobe if (uc->ret_handler) need_prep = true; + /* + * A single handler that does not mask out REMOVE, means the + * probe stays. + */ + had_handler = true; remove &= rc; } + /* + * If there were no handlers called, nobody asked for it to be removed + * but also nobody got to mask the value. Fix it up. + */ + if (!had_handler) + remove = 0; + if (need_prep && !remove) prepare_uretprobe(uprobe, regs); /* put bp at return */ - if (remove && uprobe->consumers) { - WARN_ON(!uprobe_is_active(uprobe)); + if (remove) unapply_uprobe(uprobe, current->mm); - } up_read(&uprobe->register_rwsem); }