On Mon, 31 Aug 2015, Philipp Schrader wrote: Cc'ing Paul and Steven > 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 > 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? > > 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
