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Date: Sun, 01 Jun 2008 21:47:19 +0530 From: Abhishek Sagar <sagar.abhishek@...il.com> To: rostedt@...dmis.org, Ingo Molnar <mingo@...e.hu> CC: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org> Subject: [PATCH 0/3][RFC] ftrace: track dynamic ftrace update failures Hi Steven/Ingo, In dynamic ftrace any record which fails gets freed to be recycled. This happens normally during (although not limited to) tracing of init functions. In general, failures can happen due to multiple reason, such as external patching of kernel functions, instrumentation of the mcount calls-sites, hardware error etc. As an example, in the case of kprobes if a probe is installed on the mcount call site (before being converted to NOP or after) then eventually ftrace will detect it and free the corresponding record. Kprobes however will keep on single-sepping the instruction it installed the probe on. These patches prevent freeing of records which have failed (except for init functions). This prevents re-recording of failed functions and allows tracking them so that they can be listed using a new debugfs file -> 'failures'. The main change here is preventing removal of ftrace records from ftace_hash. This way records can be looked up by their 'ip' at any time. -- Regards, Abhishek Sagar -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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