From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DEF2F272E45; Fri, 13 Jun 2025 21:10:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749849011; cv=none; b=Ka6w8RLcfIAvRzP7/5JFOpFduE6qTIhcoCSe6F1dnHEpm3cCPPCd+VjJsh0aGNb5cNUvX+xaiICegbIMnQM5gpaURWZhOYMsXUP2pvVbvnhCv8t86f6AQZ+kRG1TZIRVuqzSTT4eJEeMgTGcsYAWjnnJFZllF2ct/e0ClcIOW0k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749849011; c=relaxed/simple; bh=OmkcJNAV0hfO/+rD4d1mO4Zskm+DdbNdyEKY6x3S9ZA=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=NFIHgkYtlaCEl8vktKQGX2Tz0D31a/kKZXDcqYvbQ8QNEAbigNgzHOupWPwr5sMSWkluRBUgXC0dIjImoG2kRhrpiAex7EbSUIzAatKykAVDuYxM8wpH1ZWiNvH2rTRbWIsmuxmPgTwHYdYKOdFaYJM9vYDiZBzaHi6BHKsS4dU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=W/+KmpmN; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=B+7CxHUz; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="W/+KmpmN"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="B+7CxHUz" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1749849007; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=MuBzFJ8bax/C07ekYms0nJGiLaxwPvHrXMpn69ItGCE=; b=W/+KmpmNybGnuRoYv0AkuKtnsKYy49mDsnZqnAuVFR1iteOuBy0nacsuwGwXn52voU6/A3 rlpGxKzE17HSzJPSKGvwNQJEKPQ2IFAH0QXreT8YqKLVvYCy/n1ZCmO4AAVX15Jd+MYBUZ f078Jahg2V4fzWuEaulUv7ngS3jkX9Tek/CfN3Gn+gU1TOIbsKZQYlPliMSLFsqyqornBW lsIadsSDSfNHZTi+A/6p2ZwnwTvAdvZSMEF/OVyDAxeAFC4jk3gJJG1QVukp+FAy2z+3wo 2gYCjOHwj5rC7TfnnNYbSEVUNJgT0ejodJqurt21ADxWP4ylesQwYB2SVPEGEg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1749849007; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=MuBzFJ8bax/C07ekYms0nJGiLaxwPvHrXMpn69ItGCE=; b=B+7CxHUzslKZqG2mQ5S8cP+m4qTSW7M8mzh4mOWSOA/tKqAiCbq9U6NTQHVBHdo+sCpJ1L VBPCCiAD4jsOM0DA== To: Eugen Hristev , linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org Cc: linux-doc@vger.kernel.org, corbet@lwn.net, mingo@redhat.com, rostedt@goodmis.org, john.ogness@linutronix.de, senozhatsky@chromium.org, pmladek@suse.com, peterz@infradead.org, mojha@qti.qualcomm.com, linux-arm-kernel@lists.infradead.org, vincent.guittot@linaro.org, konradybcio@kernel.org, dietmar.eggemann@arm.com, juri.lelli@redhat.com, andersson@kernel.org Subject: Re: [RFC][PATCH 09/14] genirq: add irq_kmemdump_register In-Reply-To: References: <20250422113156.575971-1-eugen.hristev@linaro.org> <20250422113156.575971-10-eugen.hristev@linaro.org> <87h61wn2qq.ffs@tglx> <1331aa82-fee9-4788-abd9-ef741d00909e@linaro.org> Date: Fri, 13 Jun 2025 23:10:06 +0200 Message-ID: <87ikkzpcup.ffs@tglx> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Fri, Jun 13 2025 at 17:33, Eugen Hristev wrote: > On 5/7/25 13:27, Eugen Hristev wrote: >>> Let KMEMDUMP_VAR() store the size and the address of 'nr_irqs' in a >>> kmemdump specific section and then kmemdump can just walk that section >>> and dump stuff. No magic register functions and no extra storage >>> management for static/global variables. >>> >>> No? >> >> Thank you very much for your review ! I will try it out. > > I have tried this way and it's much cleaner ! thanks for the > suggestion. Welcome. > The thing that I am trying to figure out now is how to do something > similar for a dynamically allocated memory, e.g. > void *p = kmalloc(...); > and then I can annotate `p` itself, it's address and size, but what I > would also want to so dump the whole memory region pointed out by p. and > that area address and size cannot be figured out at compile time hence I > can't instantiate a struct inside the dedicated section for it. > Any suggestion on how to make that better ? Or just keep the function > call to register the area into kmemdump ? Right. For dynamically allocated memory there is obviously no compile time magic possible. But I think you can simplify the registration for dynamically allocated memory significantly. struct kmemdump_entry { void *ptr; size_t size; enum kmemdump_uids uid; }; You use that layout for the compile time table and the runtime registrations. I intentionally used an UID as that avoids string allocation and all of the related nonsense. Mapping UID to a string is a post processing problem and really does not need to be done in the kernel. The 8 character strings are horribly limited and a simple 4 byte unique id is achieving the same and saving space. Just stick the IDs into include/linux/kmemdump_ids.h and expose the content for the post processing machinery. So you want KMEMDUMP_VAR() for the compile time created table to either automatically create that ID derived from the variable name or you add an extra argument with the ID. kmemdump_init() // Use a simple fixed size array to manage this // as it avoids all the memory allocation nonsense // This stuff is neither performance critical nor does allocating // a few hundred entries create a memory consumption problem // It consumes probably way less memory than the whole IDR/XARRAY allocation // string duplication logic consumes text and data space. kmemdump_entries = kcalloc(NR_ENTRIES, sizeof(*kmemdump_entries), GFP_KERNEL); kmemdump_register(void *ptr, size_t size, enum kmemdump_uids uid) { guard(entry_mutex); entry = kmemdump_find_empty_slot(); if (!entry) return; entry->ptr = ptr; entry->size = size; entry->uid = uid; // Make this unconditional by providing a dummy backend // implementation. If the backend changes re-register all // entries with the new backend and be done with it. backend->register(entry); } kmemdump_unregister(void *ptr) { guard(entry_mutex); entry = find_entry(ptr); if (entry) { backend->unregister(entry); memset(entry, 0, sizeof(*entry); } } You get the idea. Coming back to the registration at the call site itself. struct foo = kmalloc(....); if (!foo) return; kmemdump_register(foo, sizeof(*foo), KMEMDUMP_ID_FOO); That's a code duplication shitshow. You can wrap that into: struct foo *foo = kmemdump_alloc(foo, KMEMDUMP_ID_FOO, kmalloc, ...); #define kmemdump_alloc(var, id, fn, ...) \ ({ \ void *__p = fn(##__VA_ARGS__); \ \ if (__p) \ kmemdump_register(__p, sizeof(*var), id); \ __p; }) or something daft like that. And provide the matching magic for the free side. Thoughts? Thanks, tglx