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Date: Tue, 16 Jun 2015 21:46:43 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Stephen Boyd <sboyd@...eaurora.org> Cc: John Stultz <john.stultz@...aro.org>, Nicolas Pitre <nicolas.pitre@...aro.org>, Steven Rostedt <rostedt@...dmis.org>, lkml <linux-kernel@...r.kernel.org> Subject: Re: Suspicious RCU usage at boot w/ arm ipi trace events? On Tue, Jun 16, 2015 at 05:41:29PM -0700, Stephen Boyd wrote: > On 06/16/2015 05:31 PM, Paul E. McKenney wrote: > > On Tue, Jun 16, 2015 at 05:21:59PM -0700, John Stultz wrote: > >> Not sure if I have the right folks on CC. Noticed this booting on a > >> apq8064 based system w/ 4.1-rc7 (plus a few patches that I believe are > >> unrelated). > >> > >> > >> [ 0.008796] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000 > >> [ 0.009024] Setting up static identity map for 0x80208280 - 0x802082d8 > >> [ 0.084781] CPU1: thread -1, cpu 1, socket 0, mpidr 80000001 > >> [ 0.085119] > >> [ 0.085139] =============================== > >> [ 0.085152] [ INFO: suspicious RCU usage. ] > >> [ 0.085168] 4.1.0-rc7-00033-gb5bed2f #153 Not tainted > >> [ 0.085180] ------------------------------- > >> [ 0.085195] include/trace/events/ipi.h:68 suspicious > >> rcu_dereference_check() usage! > >> [ 0.085205] > >> [ 0.085205] other info that might help us debug this: > >> [ 0.085205] > >> [ 0.085220] > >> [ 0.085220] RCU used illegally from idle CPU! > >> [ 0.085220] rcu_scheduler_active = 1, debug_locks = 0 > >> [ 0.085235] RCU used illegally from extended quiescent state! > >> [ 0.085247] no locks held by swapper/0/0. > >> [ 0.085256] > >> [ 0.085256] stack backtrace: > >> [ 0.085275] CPU: 0 PID: 0 Comm: swapper/0 Not tainted > >> 4.1.0-rc7-00033-gb5bed2f #153 > >> [ 0.085288] Hardware name: Qualcomm (Flattened Device Tree) > >> [ 0.085323] [<c0216b08>] (unwind_backtrace) from [<c02136e8>] > >> (show_stack+0x10/0x14) > >> [ 0.085348] [<c02136e8>] (show_stack) from [<c075e678>] > >> (dump_stack+0x70/0xbc) > >> [ 0.085369] [<c075e678>] (dump_stack) from [<c0215a80>] > >> (handle_IPI+0x428/0x604) > >> [ 0.085393] [<c0215a80>] (handle_IPI) from [<c020942c>] > >> (gic_handle_irq+0x54/0x5c) > >> [ 0.085423] [<c020942c>] (gic_handle_irq) from [<c0766604>] > >> (__irq_svc+0x44/0x7c) > >> [ 0.085436] Exception stack(0xc09f3f48 to 0xc09f3f90) > >> [ 0.085451] 3f40: 00000001 00000001 00000000 > >> c09f73b8 c09f4528 c0a5de9c > >> [ 0.085468] 3f60: c076b4f0 00000000 00000000 c09ef108 c0a5cec1 > >> 00000001 00000000 c09f3f90 > >> [ 0.085481] 3f80: c026bf60 c0210ab8 20000113 ffffffff > >> [ 0.085512] [<c0766604>] (__irq_svc) from [<c0210ab8>] > >> (arch_cpu_idle+0x20/0x3c) > >> [ 0.085549] [<c0210ab8>] (arch_cpu_idle) from [<c02647f0>] > >> (cpu_startup_entry+0x2c0/0x5dc) > >> [ 0.085576] [<c02647f0>] (cpu_startup_entry) from [<c099bc1c>] > >> (start_kernel+0x358/0x3c4) > >> [ 0.085600] [<c099bc1c>] (start_kernel) from [<8020807c>] (0x8020807c) > >> > >> > >> Let me know if there's any patches you'd like me to test, or if you'd > >> like config details. > > At first glance, looks like a failure to invoke irq_enter() from > > __irq_svc(), gic_handle_irq(), or handle_IPI(). > > > > Thanx, Paul > > > > The tracepoint 'trace_ipi_entry' in handle_IPI() is using RCU and we > haven't called irq_enter() yet at the point. Does this tracepoint need > to have _rcuidle() added to it? Yes, I believe that would fix this problem. Thanx, Paul -- 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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