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Message-ID: <547D27AE.5070900@slac.stanford.edu> Date: Mon, 01 Dec 2014 18:45:02 -0800 From: Till Straumann <strauman@...c.stanford.edu> To: LKML <linux-kernel@...r.kernel.org> Subject: BUG: sleeping function called from invalid context (arm CONFIG_PREEMPT_RT_FULL ) I - very reproducibly - get this 'BUG' message [ 6462.460032] Unhandled fault: external abort on non-linefetch (0x018) at 0xb6fdd000 [ 6462.460042] BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:905 [ 6462.460049] in_atomic(): 0, irqs_disabled(): 128, pid: 1488, name: ldfilt [ 6462.460053] no locks held by ldfilt/1488. [ 6462.460057] irq event stamp: 1790 [ 6462.460081] hardirqs last enabled at (1789): [<c000ed10>] no_work_pending+0x8/0x2c [ 6462.460096] hardirqs last disabled at (1790): [<c05bf834>] __dabt_usr+0x34/0x40 [ 6462.460116] softirqs last enabled at (0): [<c0021594>] copy_process.part.50+0x498/0x170c [ 6462.460124] softirqs last disabled at (0): [< (null)>] (null) [ 6462.460135] CPU: 0 PID: 1488 Comm: ldfilt Tainted: G O 3.14.12-rt9-xilinx #25 [ 6462.460161] [<c0015f6c>] (unwind_backtrace) from [<c0012cc0>] (show_stack+0x20/0x24) [ 6462.460182] [<c0012cc0>] (show_stack) from [<c05ba9ac>] (dump_stack+0x7c/0xcc) [ 6462.460208] [<c05ba9ac>] (dump_stack) from [<c00574b8>] (__might_sleep+0x1a0/0x1d8) [ 6462.460225] [<c00574b8>] (__might_sleep) from [<c05bea40>] (rt_spin_lock+0x30/0x64) [ 6462.460240] [<c05bea40>] (rt_spin_lock) from [<c0036b44>] (force_sig_info+0x38/0xe8) [ 6462.460254] [<c0036b44>] (force_sig_info) from [<c00130c0>] (arm_notify_die+0x50/0x60) [ 6462.460266] [<c00130c0>] (arm_notify_die) from [<c000845c>] (do_DataAbort+0x94/0xa8) [ 6462.460280] [<c000845c>] (do_DataAbort) from [<c05bf83c>] (__dabt_usr+0x3c/0x40) [ 6462.460285] Exception stack(0xd2e65fb0 to 0xd2e65ff8) [ 6462.460295] 5fa0: 0189d008 00000001 00001000 b6fdd000 [ 6462.460308] 5fc0: 00011cf0 b6fbc078 0189d008 00009530 00000000 be9b9ad0 ffffffff 00000000 [ 6462.460317] 5fe0: 00000000 be9b9a98 b6fa6c30 00008ad4 20000010 ffffffff [ 6462.478073] Unhandled fault: external abort on non-linefetch (0x018) at 0xb6f2a000 on my CONFIG_PREEMPT_RT_FULL system: #uname -a Linux buildroot 3.14.12-rt9 #25 SMP PREEMPT RT Fri Nov 28 09:42:05 PST 2014 armv7l GNU/Linux when accessing a mmapped, non-existing device from user-space. I'm not an ARM expert but I suspect that when the exception is taken interrupts are disabled and probably not re-enabled by the exception handler (irqs_disabled(): 128). arm_notify_die() calls force_sig_info() which may block (under RT_PREEMPT_FULL). In 'force_sig_info()' we find /* * On some archs, PREEMPT_RT has to delay sending a signal from a trap * since it can not enable preemption, and the signal code's spin_locks * turn into mutexes. Instead, it must set TIF_NOTIFY_RESUME which will * send the signal on exit of the trap. */ #ifdef ARCH_RT_DELAYS_SIGNAL_SEND and if this CPP symbol is defined there is a codepath that delays signal delivery and never blocks. Perhaps the arm support should use this facility? Unfortunately I'm not familiar enough with this CPU arch to propose a fix. Best regards - Till PS: Please CC me on any replies since I'm not a lkml subscriber; thanks. -- 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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