Messages in this thread | | | Date | Tue, 28 Feb 2017 08:52:10 +0100 | From | Peter Zijlstra <> | Subject | Re: next: runtime warning after 'locking/refcounts: Out-of-line everything' |
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On Mon, Feb 27, 2017 at 01:47:47PM -0800, Guenter Roeck wrote: > Hi Peter, > > I see the following runtime warning when running a 44x/virtex5_defconfig > image in qemu (virtex-ml507). > > refcount_t: underflow; use-after-free. > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 1 at lib/refcount.c:128 refcount_sub_and_test+0x90/0xd0 > Modules linked in: > CPU: 0 PID: 1 Comm: swapper Not tainted 4.10.0-next-20170227 #1 > task: cf81d5a0 task.stack: cf81e000 > NIP: c02100e0 LR: c02100e0 CTR: c0279970 > REGS: cf81fc90 TRAP: 0700 Not tainted (4.10.0-next-20170227) > MSR: 00029000 <CE,EE,ME> > CR: 24000022 XER: 00000000 > > GPR00: c02100e0 cf81fd40 cf81d5a0 00000026 00000000 00000000 c027a3d0 00000000 > GPR08: c05403bc 00000800 00000000 00000000 24000024 00000000 c0001ad0 00000000 > GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 c054b3c0 c0550000 > GPR24: 00000000 00000000 cf948010 00000015 00000000 00000000 cf948000 cfb1c0e8 > NIP [c02100e0] refcount_sub_and_test+0x90/0xd0 > LR [c02100e0] refcount_sub_and_test+0x90/0xd0 > Call Trace: > [cf81fd40] [c02100e0] refcount_sub_and_test+0x90/0xd0 (unreliable) > [cf81fd50] [c01f6564] kobject_put+0x34/0x90 > [cf81fd60] [c02ac240] ace_probe+0x410/0x450 > [cf81fda0] [c0293684] platform_drv_probe+0x44/0xc0 > [cf81fdc0] [c0291494] driver_probe_device+0x234/0x340 > [cf81fdf0] [c029166c] __driver_attach+0xcc/0xd0 > [cf81fe10] [c028eff8] bus_for_each_dev+0x68/0xc0 > [cf81fe40] [c0290838] bus_add_driver+0x208/0x280 > [cf81fe60] [c0292198] driver_register+0x88/0x140 > [cf81fe70] [c050be10] ace_init+0x48/0xa4 > [cf81fe90] [c0001350] do_one_initcall+0x40/0x180 > [cf81fef0] [c04f2ae0] kernel_init_freeable+0x134/0x1cc > [cf81ff30] [c0001ae4] kernel_init+0x14/0x110 > [cf81ff40] [c000c3d0] ret_from_kernel_thread+0x5c/0x64 > Instruction dump: > 40a2fff0 7f884840 7d094378 419e0044 2f89ffff 7d434850 7f0a4840 419e0018 > 4099ffd0 3c60c04b 386393f0 4820e99d <0fe00000> 80010014 38600000 38210010 > ---[ end trace 17bd7014e44a5b26 ]--- > xsysace 83600000.sysace: xsysace: error initializing device at 0x83600000 > xsysace 83600000.sysace: could not initialize device, err=-12 > xsysace: probe of 83600000.sysace failed with error -12 > Xilinx SystemACE device driver, major=254 > > The complete log is available at > http://kerneltests.org/builders/qemu-ppc-next/builds/590/steps/qemubuildcommand/logs/stdio > > Bisect points to commit 29dee3c03abc ("locking/refcounts: Out-of-line > everything'); bisect log is attached. Reverting this commit fixes the problem. > > Please let me know if there is anything I can do to help tracking down the > problem. > > [ Maybe there is a bug in the ace driver's error handler, but why is it only > seen with your patch applied ? ]
Because it unconditionally enables the WARNs, if you revert but enable CONFIG_DEBUG_REFCOUNT it should show up as well.
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