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由 Steven Rostedt (Red Hat) 提交于
Commit: c1bf08ac "ftrace: Be first to run code modification on modules" changed ftrace module notifier's priority to INT_MAX in order to process the ftrace nops before anything else could touch them (namely kprobes). This was the correct thing to do. Unfortunately, the ftrace module notifier also contains the ftrace clean up code. As opposed to the set up code, this code should be run *after* all the module notifiers have run in case a module is doing correct clean-up and unregisters its ftrace hooks. Basically, ftrace needs to do clean up on module removal, as it needs to know about code being removed so that it doesn't try to modify that code. But after it removes the module from its records, if a ftrace user tries to remove a probe, that removal will fail due as the record of that code segment no longer exists. Nothing really bad happens if the probe removal is called after ftrace did the clean up, but the ftrace removal function will return an error. Correct code (such as kprobes) will produce a WARN_ON() if it fails to remove the probe. As people get annoyed by frivolous warnings, it's best to do the ftrace clean up after everything else. By splitting the ftrace_module_notifier into two notifiers, one that does the module load setup that is run at high priority, and the other that is called for module clean up that is run at low priority, the problem is solved. Cc: stable@vger.kernel.org Reported-by: NFrank Ch. Eigler <fche@redhat.com> Acked-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
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