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[209.85.167.53]) by smtp.gmail.com with ESMTPSA id n130sm2492032lfd.213.2020.11.30.10.04.44 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Nov 2020 10:04:45 -0800 (PST) Received: by mail-lf1-f53.google.com with SMTP id z21so23334214lfe.12 for ; Mon, 30 Nov 2020 10:04:44 -0800 (PST) X-Received: by 2002:a19:ed0f:: with SMTP id y15mr9299477lfy.352.1606759484151; Mon, 30 Nov 2020 10:04:44 -0800 (PST) MIME-Version: 1.0 References: <160665707945.2808.5384034634184489471.tglx@nanos> <160665708065.2808.15317906761841446715.tglx@nanos> <20201130075651.GJ2414@hirez.programming.kicks-ass.net> <20201130125211.GN2414@hirez.programming.kicks-ass.net> <20201130130315.GJ3092@hirez.programming.kicks-ass.net> In-Reply-To: <20201130130315.GJ3092@hirez.programming.kicks-ass.net> From: Linus Torvalds Date: Mon, 30 Nov 2020 10:04:27 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT pull] locking/urgent for v5.10-rc6 To: Peter Zijlstra Cc: Sven Schnelle , Thomas Gleixner , "Paul E. McKenney" , Linux Kernel Mailing List , "the arch/x86 maintainers" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 30, 2020 at 5:03 AM Peter Zijlstra wrote: > > > But but but... > > > > do_idle() # IRQs on > > local_irq_disable(); # IRQs off > > defaul_idle_call() # IRQs off > lockdep_hardirqs_on(); # IRQs off, but lockdep things they're on > > arch_cpu_idle() # IRQs off > > enabled_wait() # IRQs off > > raw_local_save() # still off > > psw_idle() # very much off > > ext_int_handler # get an interrupt ?!?! > rcu_irq_enter() # lockdep thinks IRQs are on <- FAIL > > I can't much read s390 assembler, but ext_int_handler() has a > TRACE_IRQS_OFF, which would be sufficient to re-align the lockdep state > with the actual state, but there's some condition before it, what's that > test and is that right? I think that "psw_idle()" enables interrupts, exactly like x86 does. See my previous email. But no, I can't read s390 asm either. IBM is notorious for making up odd IBM-only incomprehensible names. When "oi" means "or immediate", I personally start suspecting that there were some "happy drugs" involved. To make matters worse, some of the assembly code in psw_idle isn't even assembly code, it's machine code, with "BPON" being an alternative instruction definition with just the hex encoding for the machine code instruction rather than any actual human-legible instruction encoding. Of course, when the "human-legible" instructions are "oi", I guess hex codes aren't all that much less legible.. s390 programmers must be some super-human breed. Or, alternatively, they are munching happy pills by the truck-load to get over the pain ;) Linus