Messages in this thread Patch in this message | | | Date | Thu, 31 Jan 2013 20:18:19 +0100 | From | Oleg Nesterov <> | Subject | [PATCH 2/6] uprobes/tracing: Fully initialize uprobe_trace_consumer before uprobe_register() |
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probe_event_enable() does uprobe_register() and only after that sets utc->tu and tu->consumer/flags. This can race with uprobe_dispatcher() which can miss these assignments or see them out of order. Nothing really bad can happen, but this doesn't look clean/safe.
And this does not allow to use uprobe_consumer->filter() we are going to add, it is called by uprobe_register() and it needs utc->tu.
Change this code to initialize everything before uprobe_register(), and reset tu->consumer/flags if it fails. We can't race with event_disable(), the caller holds event_mutex, and if we could the code would be wrong anyway.
In fact I think uprobe_trace_consumer should die, it buys nothing but complicates the code. We can simply add uprobe_consumer into trace_uprobe.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> --- kernel/trace/trace_uprobe.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 6563f00..7b75949 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -547,17 +547,18 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag) return -EINTR; utc->cons.handler = uprobe_dispatcher; + utc->tu = tu; + tu->consumer = utc; + tu->flags |= flag; + ret = uprobe_register(tu->inode, tu->offset, &utc->cons); if (ret) { + tu->consumer = NULL; + tu->flags &= ~flag; kfree(utc); - return ret; } - tu->flags |= flag; - utc->tu = tu; - tu->consumer = utc; - - return 0; + return ret; } static void probe_event_disable(struct trace_uprobe *tu, int flag) -- 1.5.5.1
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