On Tue, 1 Sep 2015 17:35:23 +0200 (CEST) Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > On Mon, 31 Aug 2015, Philipp Schrader wrote: > > Cc'ing Paul and Steven Not sure if we were actually Cc'd (reading this from my linux-rt-users folder) > > > Hi all, > > > > I've got a real-time kernel on a DRA7 evaluation module (EVM). > > Very early in the boot process I get the following splat. > > > > [ 0.055073] > > [ 0.055076] =============================== > > [ 0.055079] [ INFO: suspicious RCU usage. ] > > [ 0.055084] 4.1.6+ #2 Not tainted > > [ 0.055086] ------------------------------- > > [ 0.055090] include/trace/events/hist.h:31 suspicious Hmm, the histogram code in -rt, needs a rewrite :-/ I haven't had time to do so. But it's definitely on my TODO list. > > rcu_dereference_check() usage! > > [ 0.055093] > > [ 0.055093] other info that might help us debug this: > > [ 0.055093] > > [ 0.055097] > > [ 0.055097] RCU used illegally from idle CPU! > > [ 0.055097] rcu_scheduler_active = 1, debug_locks = 1 > > [ 0.055100] RCU used illegally from extended quiescent state! > > [ 0.055104] no locks held by swapper/0/0. > > [ 0.055106] > > [ 0.055106] stack backtrace: > > [ 0.055112] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.1.6+ #2 > > [ 0.055116] Hardware name: Generic DRA74X (Flattened Device Tree) > > [ 0.055130] [<c00196b8>] (unwind_backtrace) from [<c001515c>] > > (show_stack+0x20/0x24) > > [ 0.055146] [<c001515c>] (show_stack) from [<c07bc408>] > > (dump_stack+0x84/0xa0) > > [ 0.055160] [<c07bc408>] (dump_stack) from [<c009bc38>] > > (lockdep_rcu_suspicious+0xb0/0x110) > > [ 0.055172] [<c009bc38>] (lockdep_rcu_suspicious) from [<c01246c4>] > > (time_hardirqs_off+0x2b8/0x3c8) > > [ 0.055184] [<c01246c4>] (time_hardirqs_off) from [<c009a218>] > > (trace_hardirqs_off_caller+0x2c/0xf4) > > [ 0.055194] [<c009a218>] (trace_hardirqs_off_caller) from > > [<c009a2f4>] (trace_hardirqs_off+0x14/0x18) > > [ 0.055204] [<c009a2f4>] (trace_hardirqs_off) from [<c00c7ecc>] > > (rcu_idle_enter+0x78/0xcc) > > [ 0.055213] [<c00c7ecc>] (rcu_idle_enter) from [<c0093eb0>] > > (cpu_startup_entry+0x190/0x518) > > [ 0.055222] [<c0093eb0>] (cpu_startup_entry) from [<c07b95b4>] > > (rest_init+0x13c/0x17c) > > [ 0.055231] [<c07b95b4>] (rest_init) from [<c0b32c74>] > > (start_kernel+0x320/0x380) > > [ 0.055238] [<c0b32c74>] (start_kernel) from [<8000807c>] (0x8000807c) > > > > I'm not sure how to debug this; I'm still reading up on RCUs. Pretty > > nifty ideas. > > > > Looking at include/trace/events/hist.h it appears line 31 is the end > > of a TRACE_EVENT macro usage. > > Does that mean the macro is using RCU improperly somehow? I think this needs to be a trace_*_rcu_idle() call. That is, I bet the tracepoint was triggered when rcu wasn't watching. -- Steve > > > > Thanks, > > Philipp > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html