Hi Andy, Sorry for late reply. On 05/29/2015 09:07 AM, Andy Lutomirski wrote:
> On Wed, May 27, 2015 at 6:20 PM, Gu Zheng <guz.f...@cn.fujitsu.com> wrote: >> ping... >> >> On 05/22/2015 06:13 PM, Gu Zheng wrote: >> >>> The following lockdep warning occurs when running with 4.1.0-rc3: >>> [ 3.178000] ------------[ cut here ]------------ >>> [ 3.183000] WARNING: CPU: 128 PID: 0 at kernel/locking/lockdep.c:2755 >>> lockdep_trace_alloc+0xdd/0xe0() >>> [ 3.193000] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)) >>> [ 3.199000] Modules linked in: >>> >>> [ 3.203000] CPU: 128 PID: 0 Comm: swapper/128 Not tainted 4.1.0-rc3 #70 >>> [ 3.221000] 0000000000000000 2d6601fb3e6d4e4c ffff88086fd5fc38 >>> ffffffff81773f0a >>> [ 3.230000] 0000000000000000 ffff88086fd5fc90 ffff88086fd5fc78 >>> ffffffff8108c85a >>> [ 3.238000] ffff88086fd60000 0000000000000092 ffff88086fd60000 >>> 00000000000000d0 >>> [ 3.246000] Call Trace: >>> [ 3.249000] [<ffffffff81773f0a>] dump_stack+0x4c/0x65 >>> [ 3.255000] [<ffffffff8108c85a>] warn_slowpath_common+0x8a/0xc0 >>> [ 3.261000] [<ffffffff8108c8e5>] warn_slowpath_fmt+0x55/0x70 >>> [ 3.268000] [<ffffffff810ee24d>] lockdep_trace_alloc+0xdd/0xe0 >>> [ 3.274000] [<ffffffff811cda0d>] __alloc_pages_nodemask+0xad/0xca0 >>> [ 3.281000] [<ffffffff810ec7ad>] ? __lock_acquire+0xf6d/0x1560 >>> [ 3.288000] [<ffffffff81219c8a>] alloc_page_interleave+0x3a/0x90 >>> [ 3.295000] [<ffffffff8121b32d>] alloc_pages_current+0x17d/0x1a0 >>> [ 3.301000] [<ffffffff811c869e>] ? __get_free_pages+0xe/0x50 >>> [ 3.308000] [<ffffffff811c869e>] __get_free_pages+0xe/0x50 >>> [ 3.314000] [<ffffffff8102640b>] init_espfix_ap+0x17b/0x320 >>> [ 3.320000] [<ffffffff8105c691>] start_secondary+0xf1/0x1f0 >>> [ 3.327000] ---[ end trace 1b3327d9d6a1d62c ]--- >>> >>> This seems a mis-warning by lockdep, as we alloc pages with GFP_KERNEL in >>> init_espfix_ap() which is called before enabled local irq, and the lockdep >>> sub-system considers this behaviour as allocating memory with GFP_FS with >>> local irq disabled, then trigger the warning as mentioned about. >>> >>> Though we could allocate them on the boot CPU side and hand them over to >>> the secondary CPU, but it seems a waste if some of cpus are still offline. >>> As there is no need to these pages(espfix stack) until we try to run user >>> code, so we can postpone the initialization of espfix stack after cpu >>> booted to avoid the noise. > > Does this pass the sigreturn_32 test on both 32-bit and 64-bit kernels > and sigreturn_64 test on 64-bit kernels? (The test is in > tools/testing/selftests/x86.) If so, looks good to me. It failed the test. There seems a bug in this patch, it alloc espfix stack in the do_boot_cpu routine, not in the context of target cpu that we want to boot up, so the simple change is wrong here. I will send the v2 version soon, and it passed the tests you mentioned above. Thanks again for your comments and suggestion. Regards, Gu > > --Andy > >>> >>> Signed-off-by: Gu Zheng <guz.f...@cn.fujitsu.com> >>> --- >>> arch/x86/kernel/smpboot.c | 14 +++++++------- >>> 1 file changed, 7 insertions(+), 7 deletions(-) >>> >>> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c >>> index 50e547e..3ce05de 100644 >>> --- a/arch/x86/kernel/smpboot.c >>> +++ b/arch/x86/kernel/smpboot.c >>> @@ -240,13 +240,6 @@ static void notrace start_secondary(void *unused) >>> check_tsc_sync_target(); >>> >>> /* >>> - * Enable the espfix hack for this CPU >>> - */ >>> -#ifdef CONFIG_X86_ESPFIX64 >>> - init_espfix_ap(); >>> -#endif >>> - >>> - /* >>> * We need to hold vector_lock so there the set of online cpus >>> * does not change while we are assigning vectors to cpus. Holding >>> * this lock ensures we don't half assign or remove an irq from a cpu. >>> @@ -901,6 +894,13 @@ static int do_boot_cpu(int apicid, int cpu, struct >>> task_struct *idle) >>> } >>> } >>> >>> + /* >>> + * Enable the espfix hack for this CPU >>> + */ >>> +#ifdef CONFIG_X86_ESPFIX64 >>> + init_espfix_ap(); >>> +#endif >>> + >>> /* mark "stuck" area as not stuck */ >>> *trampoline_status = 0; >>> >> >> > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/