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Tue, 20 Oct 2020 11:18:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603192695; bh=2qnYnLk0zJvDuNzY1+fnwuJKS+83hTZg+127pZd/L48=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=fvaDeVXK8LzzgZcqRwloQEBDUr1ntce3eaLBO60GaANnX4ya6mAXxQq5BL/h3dXls NBrLZnQB1pZx+2dia75dMLVezlxHhAGpbxzWmTqMpUBeuRmTwHs+0lX1yJxfgsGpFD FHg8mpftGtGTmJkT34NzFv3G6zlZJfFMUlRC5EFY= Received: by mail-lf1-f41.google.com with SMTP id l2so1638395lfk.0; Tue, 20 Oct 2020 04:18:14 -0700 (PDT) X-Gm-Message-State: AOAM531TlydtS5iJrdYN7pAvucRot5T07niR2IWNXN6psqQ+hTsAofqg m1TFrpgS8cGK6BGrNW1PjmCtHCtLKWDg8WuoKkw= X-Received: by 2002:a19:6b10:: with SMTP id d16mr716908lfa.121.1603192692785; Tue, 20 Oct 2020 04:18:12 -0700 (PDT) MIME-Version: 1.0 References: <1602918377-23573-1-git-send-email-guoren@kernel.org> <1602918377-23573-10-git-send-email-guoren@kernel.org> In-Reply-To: From: Guo Ren Date: Tue, 20 Oct 2020 19:18:01 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v4 9/9] riscv: Fixup lockdep_assert_held(&text_mutex) in patch_insn_write To: Atish Patra Cc: Zong Li , Palmer Dabbelt , Paul Walmsley , Masami Hiramatsu , Alan Kao , Steven Rostedt , =?UTF-8?Q?Patrick_St=C3=A4hlin?= , Guo Ren , Anup Patel , "linux-kernel@vger.kernel.org List" , linux-csky@vger.kernel.org, Greentime Hu , linux-riscv Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 20, 2020 at 2:54 AM Atish Patra wrote: > > On Sat, Oct 17, 2020 at 12:07 AM wrote: > > > > From: Guo Ren > > > > It will cause warning messages: > > echo function_graph > /sys/kernel/debug/tracing/current_tracer > > [ 47.691397] ------------[ cut here ]------------ > > [ 47.692899] WARNING: CPU: 0 PID: 11 at arch/riscv/kernel/patch.c:63 patch_insn_write+0x182/0x19a > > [ 47.694483] Modules linked in: > > [ 47.695754] CPU: 0 PID: 11 Comm: migration/0 Not tainted 5.9.0-11367-g1054335 #132 > > [ 47.698228] epc: ffffffe000204530 ra : ffffffe00020452c sp : ffffffe0023ffc20 gp : ffffffe0013e1fe0 tp : ffffffe0023e4e00 t0 : 0000000000000000 > > [ 47.701872] t1 : 000000000000000e t2 : 000000000000001b s0 : ffffffe0023ffc70 s1 : ffffffe000206850 a0 : 0000000000000000 a1 : ffffffffffffffff > > [ 47.705550] a2 : 0000000000000000 a3 : ffffffe03af7c5e8 a4 : 0000000000000000 a5 : 0000000000000000 a6 : 0000000000000000 a7 : 00000000150b02d8 > > [ 47.709159] s2 : 0000000000000008 s3 : 0000000000000858 s4 : ffffffe0023ffc98 s5 : 0000000000000850 s6 : 0000000000000003 s7 : 0000000000000002 > > [ 47.714135] s8 : 0000000000000004 s9 : 0000000000000001 s10: 0000000000000001 s11: 0000000000000003 t3 : ffffffffffffe000 t4 : 0000000000d86254 > > [ 47.716574] t5 : 0000000000000005 t6 : 0000000000040000status: 0000000000000100 badaddr: 0000000000000000 cause: 0000000000000003 > > [ 47.720019] CPU: 0 PID: 11 Comm: migration/0 Not tainted 5.9.0-11367-g1054335 #132 > > [ 47.722074] Call Trace: > > [ 47.722561] [] walk_stackframe+0x0/0xc2 > > [ 47.724608] [] show_stack+0x46/0x52 > > [ 47.726246] [] dump_stack+0x90/0xb6 > > [ 47.727672] [] __warn+0x98/0xfa > > [ 47.729131] [] report_bug+0xaa/0x11e > > [ 47.730624] [] do_trap_break+0x96/0xfe > > [ 47.732448] [] ret_from_exception+0x0/0x14 > > [ 47.734341] [] patch_insn_write+0x17e/0x19a > > [ 47.737235] irq event stamp: 39 > > [ 47.738521] hardirqs last enabled at (39): [] _save_context+0xa2/0xe6 > > [ 47.741055] hardirqs last disabled at (38): [] multi_cpu_stop+0x130/0x166 > > [ 47.743551] softirqs last enabled at (0): [] copy_process+0x430/0x1316 > > [ 47.746031] softirqs last disabled at (0): [<0000000000000000>] 0x0 > > [ 47.748617] ---[ end trace 88a1054faa6524ef ]--- > > > > Because the path of stop_machine(__ftrace_modify_code)-> > > ftrace_modify_all_code->...->patch_insn_write has no pair of > > lock&unlock text_mutex, so we shouldn't put assert here. > > > > What platform are you testing ? We are seeing a crash while enabling > any of the tracers multiple times > on Qemu/HiFive Unleashed. I use qemu for testing. I've changed dynamic ftrace mechanism from mcount to -fpatchable-entry. The problem is made by the lockdep checking of text_mutex. > > http://lists.infradead.org/pipermail/linux-riscv/2020-October/002354.html > > As per the thread, Zong agreed to take a look into that. > @Zong Li : Do you have any update regarding the ftrace issue. > > > Signed-off-by: Guo Ren > > --- > > arch/riscv/kernel/patch.c | 7 ------- > > 1 file changed, 7 deletions(-) > > > > diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c > > index 0b55287..2ee5063 100644 > > --- a/arch/riscv/kernel/patch.c > > +++ b/arch/riscv/kernel/patch.c > > @@ -55,13 +55,6 @@ static int patch_insn_write(void *addr, const void *insn, size_t len) > > bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE; > > int ret; > > > > - /* > > - * Before reaching here, it was expected to lock the text_mutex > > - * already, so we don't need to give another lock here and could > > - * ensure that it was safe between each cores. > > - */ > > - lockdep_assert_held(&text_mutex); > > - > > if (across_pages) > > patch_map(addr + len, FIX_TEXT_POKE1); > > > > -- > > 2.7.4 > > > > > > _______________________________________________ > > linux-riscv mailing list > > linux-riscv@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-riscv > > > > -- > Regards, > Atish -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/