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Date: Wed, 16 Jul 2014 07:17:07 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Ingo Molnar <mingo@...nel.org> Cc: linux-kernel@...r.kernel.org, fabf@...net.be, bobby.prani@...il.com, davidshan@...cent.com, joe@...ches.com, keescook@...omium.org, Peter Zijlstra <a.p.zijlstra@...llo.nl> Subject: Re: [GIT PULL rcu/next] RCU commits for 3.17 On Wed, Jul 16, 2014 at 03:13:22PM +0200, Ingo Molnar wrote: > > * Ingo Molnar <mingo@...nel.org> wrote: > > > > > * Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote: > > > > > Hello, Ingo, > > > > > > The changes in this series include: > > > > > > 1. Update RCU documentation. These were posted to LKML at > > > https://lkml.org/lkml/2014/7/7/650. > > > > > > 2. Miscellaneous fixes. These were posted to LKML at > > > https://lkml.org/lkml/2014/7/7/678. > > > > > > 3. Maintainership changes. These were posted to LKML at > > > https://lkml.org/lkml/2014/7/7/713, with a couple of > > > additional at https://lkml.org/lkml/2014/7/3/812 and > > > https://lkml.org/lkml/2014/6/2/585. > > > > > > 4. Torture-test updates. These were posted to LKML at > > > https://lkml.org/lkml/2014/7/7/816. > > > > > > 5. Callback-offloading changes. These were posted to LKML at > > > https://lkml.org/lkml/2014/7/7/1007. > > > > > > All of these have been exposed to -next testing. > > JFYI, the attached x86 (rand!-) config crashes on early bootup: > > [ 0.000000] RCU: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=2 > [ 0.000000] ------------[ cut here ]------------ > [ 0.000000] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/cpu/common.c:1439 warn_pre_alternatives+0x1e/0x20() > [ 0.000000] You're using static_cpu_has before alternatives have run! > [ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.16.0-rc5+ #236363 > [ 0.000000] Hardware name: System manufacturer System Product Name/A8N-E, BIOS ASUS A8N-E ACPI BIOS Revision 1008 08/22/2005 > [ 0.000000] 0000000000000000 ffffffff82787c60 ffffffff81ff4ec0 ffffffff82787ca8 > [ 0.000000] ffffffff82787c98 ffffffff810651ac ffffffff81011531 ffffffff82787e48 > [ 0.000000] 0000000000000000 0000000000000000 ffffffff827cf880 ffffffff82787cf8 > [ 0.000000] Call Trace: > [ 0.000000] [<ffffffff81ff4ec0>] dump_stack+0x4d/0x66 > [ 0.000000] [<ffffffff810651ac>] warn_slowpath_common+0x7a/0x93 > [ 0.000000] [<ffffffff81011531>] ? warn_pre_alternatives+0x1e/0x20 > [ 0.000000] [<ffffffff81065239>] warn_slowpath_fmt+0x4c/0x4e > [ 0.000000] [<ffffffff82005817>] ? irq_return+0x7/0x7 > [ 0.000000] [<ffffffff81011531>] warn_pre_alternatives+0x1e/0x20 > [ 0.000000] [<ffffffff81033d31>] __do_page_fault+0xc3/0x43f > [ 0.000000] [<ffffffff81005347>] ? print_context_stack+0x6a/0xb6 > [ 0.000000] [<ffffffff810045f1>] ? dump_trace+0x27d/0x294 > [ 0.000000] [<ffffffff815b185b>] ? number.isra.1+0x127/0x22c > [ 0.000000] [<ffffffff8109abe2>] ? print_time.part.5+0x58/0x5c > [ 0.000000] [<ffffffff81086a9a>] ? sched_clock_cpu+0x11/0xb9 > [ 0.000000] [<ffffffff810340ef>] do_page_fault+0x1e/0x54 > [ 0.000000] [<ffffffff82005817>] ? irq_return+0x7/0x7 > [ 0.000000] [<ffffffff82006872>] page_fault+0x22/0x30 > [ 0.000000] [<ffffffff815b65fa>] ? __bitmap_or+0x15/0x28 > [ 0.000000] [<ffffffff82c876f0>] rcu_init_one+0x4c0/0x55d > [ 0.000000] [<ffffffff82c87b00>] rcu_init+0x270/0x2da > [ 0.000000] [<ffffffff82c6ec82>] start_kernel+0x24f/0x4d2 > [ 0.000000] [<ffffffff82c6e841>] ? set_init_arg+0x53/0x53 > [ 0.000000] [<ffffffff82c6e453>] x86_64_start_reservations+0x2a/0x2c > [ 0.000000] [<ffffffff82c6e546>] x86_64_start_kernel+0xf1/0xf4 > [ 0.000000] ---[ end trace 4650963e41188009 ]--- > [ 0.000000] BUG: unable to handle kernel NULL pointer dereference at (null) > [ 0.000000] IP: [<ffffffff815b65fa>] __bitmap_or+0x15/0x28 > [ 0.000000] PGD 0 > [ 0.000000] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC > [ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 3.16.0-rc5+ #236363 > [ 0.000000] Hardware name: System manufacturer System Product Name/A8N-E, BIOS ASUS A8N-E ACPI BIOS Revision 1008 08/22/2005 > [ 0.000000] task: ffffffff827a3480 ti: ffffffff82784000 task.ti: ffffffff82784000 > [ 0.000000] RIP: 0010:[<ffffffff815b65fa>] [<ffffffff815b65fa>] __bitmap_or+0x15/0x28 > [ 0.000000] RSP: 0000:ffffffff82787ef8 EFLAGS: 00010002 > [ 0.000000] RAX: 0000000000000000 RBX: 00000000ffffffff RCX: 0000000000000001 > [ 0.000000] RDX: 0000000000000000 RSI: ffff880000019800 RDI: ffff880000019800 > [ 0.000000] RBP: ffffffff82787ef8 R08: 0000000000000000 R09: 0000000000000000 > [ 0.000000] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff827cf880 > [ 0.000000] R13: 0000000000000002 R14: ffffffff827cf880 R15: 00000000001cd000 > [ 0.000000] FS: 0000000000000000(0000) GS:ffff88003f800000(0000) knlGS:0000000000000000 > [ 0.000000] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > [ 0.000000] CR2: 0000000000000000 CR3: 000000000279e000 CR4: 00000000000006b0 > [ 0.000000] Stack: > [ 0.000000] ffffffff82787f50 ffffffff82c876f0 ffffffff83b7e7a0 0000000000000001 > [ 0.000000] 0000000000000082 0000000200000000 00000000ffffffff ffffffff82d37920 > [ 0.000000] ffff88003ffbba40 ffffffff82d3e890 0000000000000000 ffffffff82787f80 > [ 0.000000] Call Trace: > [ 0.000000] [<ffffffff82c876f0>] rcu_init_one+0x4c0/0x55d > [ 0.000000] [<ffffffff82c87b00>] rcu_init+0x270/0x2da > [ 0.000000] [<ffffffff82c6ec82>] start_kernel+0x24f/0x4d2 > [ 0.000000] [<ffffffff82c6e841>] ? set_init_arg+0x53/0x53 > [ 0.000000] [<ffffffff82c6e453>] x86_64_start_reservations+0x2a/0x2c > [ 0.000000] [<ffffffff82c6e546>] x86_64_start_kernel+0xf1/0xf4 > [ 0.000000] Code: 4c 89 04 c7 4d 09 c1 48 ff c0 eb e8 31 c0 4d 85 c9 0f 95 c0 5d c3 55 48 63 c9 31 c0 48 83 c1 3f 48 89 e5 48 c1 e9 06 39 c1 7e 11 <4c> 8b 04 c2 4c 0b 04 c6 4c 89 04 c7 48 ff c0 eb eb 5d c3 55 48 > [ 0.000000] RIP [<ffffffff815b65fa>] __bitmap_or+0x15/0x28 > [ 0.000000] RSP <ffffffff82787ef8> > [ 0.000000] CR2: 0000000000000000 > [ 0.000000] ---[ end trace 4650963e4118800a ]--- > [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task! > [ 0.000000] Rebooting in 1 seconds..Press any key to enter the menu > > Excluding the new RCU bits from tip:master makes it boot. > > Any idea what's wrong? Looks like you have a setup that has NO_HZ_FULL=y, but that somehow avoids having a non-NULL tick_nohz_full_mask at rcu_init() time. But you probably knew that already. And of course when I test locally with the same RCU-related and NO_HZ_FULL-related configs, it all works just fine. Perhaps there is some interaction with some other code in -tip. So let's see... Now your .config has CONFIG_NO_HZ_FULL_ALL=y and therefore also has CONFIG_RCU_NOCB_CPU_ALL=y. In that case, there is no point in doing the cpumask_or() because all the bits are already set. So the only time that this cpumask_or() matters is when CONFIG_RCU_NOCB_CPU_ALL==n and an explicit nohz_full= mask was specified at boot time. So one reasonable change is to replace the #ifndef guarding the cpumask_or() with: #if defined(CONFIG_NO_HZ_FULL) && !defined(CONFIG_RCU_NOCB_CPU_ALL) I am now looking to see how tick_nohz_full_mask might be NULL in this situation. Depending on what I find, I might insert a check for that. 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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