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Wed, 02 Sep 2020 06:57:38 -0700 (PDT) Subject: Re: [PATCH v2 11/11] lockdep,trace: Expose tracepoints To: peterz@infradead.org Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, will@kernel.org, npiggin@gmail.com, elver@google.com, jgross@suse.com, paulmck@kernel.org, rostedt@goodmis.org, rjw@rjwysocki.net, joel@joelfernandes.org, svens@linux.ibm.com, tglx@linutronix.de, ulf.hansson@linaro.org, viresh.kumar@linaro.org, vincent.guittot@linaro.org References: <20200821084738.508092956@infradead.org> <20200821085348.782688941@infradead.org> <20200902035146.GA45826@roeck-us.net> <20200902085636.GV1362448@hirez.programming.kicks-ass.net> From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= Message-ID: Date: Wed, 2 Sep 2020 06:57:36 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200902085636.GV1362448@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/2/20 1:56 AM, peterz@infradead.org wrote: > On Tue, Sep 01, 2020 at 08:51:46PM -0700, Guenter Roeck wrote: > >> [ 27.056457] include/trace/events/lock.h:13 suspicious rcu_dereference_check() usage! > >> [ 27.057006] Hardware name: Generic OMAP3-GP (Flattened Device Tree) >> [ 27.057098] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) >> [ 27.057189] [] (show_stack) from [] (dump_stack+0xd8/0xf8) >> [ 27.057312] [] (dump_stack) from [] (lock_acquire+0x4d8/0x4dc) >> [ 27.057464] [] (lock_acquire) from [] (_raw_spin_lock_irqsave+0x58/0x74) >> [ 27.057617] [] (_raw_spin_lock_irqsave) from [] (pwrdm_lock+0x10/0x18) >> [ 27.057739] [] (pwrdm_lock) from [] (clkdm_deny_idle+0x10/0x24) >> [ 27.057891] [] (clkdm_deny_idle) from [] (omap3_enter_idle_bm+0xd4/0x1b8) >> [ 27.058044] [] (omap3_enter_idle_bm) from [] (cpuidle_enter_state+0x16c/0x620) > > ARM cpuidle is a trainwreck :/ > > So it looks like we have: > > - clkdm_ > - pwrdm_ > - cpu_pm_ > - pm_runtime_ > > In that approximate order, and then there's the coupled idle muck. > Sometimes cpuidle core calls cpu_pm_*(), but mostly it's sprinkled > around in drivers. > > How about we unconditionally kill tracing when RCU is idle? Yes this is > a hack, and we really should turn it into a WARN in due time. > > The thing is, we're shutting down clock/power domains and god knows > what, the CPU is in a crap state, we'll not take interrupts, but tracing > must happen! Hell no. > > Let's make the rule that if you want something traced, you get to pull > it out of the cpuidle driver and stick it in the generic code with a > CPUIDLE_FLAG, before rcu_idle_enter(). > > Totally untested patch below.. > Unfortunately, that patch does not make a difference; I still see the same tracebacks with it applied. Guenter > --- > > diff --git a/include/linux/preempt.h b/include/linux/preempt.h > index 7d9c1c0e149c..878bac893e41 100644 > --- a/include/linux/preempt.h > +++ b/include/linux/preempt.h > @@ -27,17 +27,20 @@ > * SOFTIRQ_MASK: 0x0000ff00 > * HARDIRQ_MASK: 0x000f0000 > * NMI_MASK: 0x00f00000 > + * RCUIDLE_MASK: 0x01000000 > * PREEMPT_NEED_RESCHED: 0x80000000 > */ > #define PREEMPT_BITS 8 > #define SOFTIRQ_BITS 8 > #define HARDIRQ_BITS 4 > #define NMI_BITS 4 > +#define RCUIDLE_BITS 1 > > #define PREEMPT_SHIFT 0 > #define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS) > #define HARDIRQ_SHIFT (SOFTIRQ_SHIFT + SOFTIRQ_BITS) > #define NMI_SHIFT (HARDIRQ_SHIFT + HARDIRQ_BITS) > +#define RCUIDLE_SHIFT (NMI_SHIFT + NMI_BITS) > > #define __IRQ_MASK(x) ((1UL << (x))-1) > > @@ -45,11 +48,13 @@ > #define SOFTIRQ_MASK (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT) > #define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT) > #define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT) > +#define RCUIDLE_MASK (__IRQ_MASK(RCUIDLE_BITS) << RCUIDLE_SHIFT) > > #define PREEMPT_OFFSET (1UL << PREEMPT_SHIFT) > #define SOFTIRQ_OFFSET (1UL << SOFTIRQ_SHIFT) > #define HARDIRQ_OFFSET (1UL << HARDIRQ_SHIFT) > #define NMI_OFFSET (1UL << NMI_SHIFT) > +#define RCUIDLE_OFFSET (1UL << RCUIDLE_SHIFT) > > #define SOFTIRQ_DISABLE_OFFSET (2 * SOFTIRQ_OFFSET) > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index 598fec9f9dbf..997472c662c4 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -164,7 +164,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) > void *__data; \ > int __maybe_unused __idx = 0; \ > \ > - if (!(cond)) \ > + if (!(cond) || (preempt_count() & RCUIDLE_MASK)) \ > return; \ > \ > /* srcu can't be used from NMI */ \ > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 8ce77d9ac716..ad9fb4f12c63 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -269,6 +269,8 @@ static noinstr void rcu_dynticks_eqs_enter(void) > /* Better not have special action (TLB flush) pending! */ > WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && > (seq & RCU_DYNTICK_CTRL_MASK)); > + > + __preempt_count_add(RCUIDLE_OFFSET); > } > > /* > @@ -281,6 +283,8 @@ static noinstr void rcu_dynticks_eqs_exit(void) > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > int seq; > > + __preempt_count_sub(RCUIDLE_OFFSET); > + > /* > * CPUs seeing atomic_add_return() must see prior idle sojourns, > * and we also must force ordering with the next RCU read-side >