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From: Joe Perches <joe@perches.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Laight <David.Laight@aculab.com>,
	Petr Mladek <pmladek@suse.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Sergey Senozhatsky <senozhatsky@chromium.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Matthew Wilcox <willy@infradead.org>,
	Miguel Ojeda <ojeda@kernel.org>,
	Kent Overstreet <kent.overstreet@gmail.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [RFC[ Alloc in vsprintf
Date: Sun, 26 Jun 2022 13:39:01 -0700	[thread overview]
Message-ID: <93ab94ec92497af13c563c52fc7e1f7f81dac333.camel@perches.com> (raw)
In-Reply-To: <CAHk-=whwyxSpzgr+roEr7_V5wVenw9fV3EOAZhAYCAuRdEyChQ@mail.gmail.com>

On Sun, 2022-06-26 at 13:19 -0700, Linus Torvalds wrote:
> On Sun, Jun 26, 2022 at 12:53 PM Joe Perches <joe@perches.com> wrote:
> > 
> > In a reply to the printbufs thread, I wrote a proposal to use an
> > alloc to reduce stack in vsprintf when CONFIG_KALLSYMS is enabled.
> > 
> > No one has replied to this but I think it's somewhat sensible.
> 
> I think that's a bad idea.

Somewhat sensible not sensible...

> Those things are *literally* called from panic situations, which may
> be while holding core memory allocation locks, or similar.

True, and special_hex_number was used on alloc failure.

> Now, you are correct that the stack buffer is annoying. But I think
> the proper way to fix that is to say "we already *have* the target
> buffer, let's use it".

OK, and that's true for all the temp stack buffers in every %p<foo>.

> That does require teaching the sprint_symbol() functions that they
> need to take a "length of buffer" and return how much they used, but
> that would seem to be a sensible thing anyway, and what the code
> should always have done?

Unnecessary stack and/or unnecessary buffers for printbufs are
just unnecessary. 

> It's bad policy to just pass in a buffer without length, and I think
> it was always broken. Nasty. That KSYM_SYMBOL_LEN is magically taking
> care of it all, but it's ugly as heck, wouldn't you say?

Yup.


  reply	other threads:[~2022-06-26 20:39 UTC|newest]

Thread overview: 86+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-20  0:41 [PATCH v4 00/34] Printbufs - new data structure for building strings Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 01/34] lib/printbuf: New data structure for printing strings Kent Overstreet
2022-06-20  4:44   ` David Laight
2022-06-20 15:30     ` Kent Overstreet
2022-06-20 15:53       ` David Laight
2022-06-20 16:14         ` Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 02/34] lib/string_helpers: Convert string_escape_mem() to printbuf Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 03/34] vsprintf: Convert " Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 04/34] lib/hexdump: " Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 05/34] vsprintf: %pf(%p) Kent Overstreet
2022-06-21  7:04   ` Rasmus Villemoes
2022-06-21  7:51     ` Kent Overstreet
2022-06-21  8:47       ` Rasmus Villemoes
2022-06-21 11:11     ` David Laight
2022-06-20  0:42 ` [PATCH v4 06/34] lib/string_helpers: string_get_size() now returns characters wrote Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 07/34] lib/printbuf: Heap allocation Kent Overstreet
2022-06-21  7:58   ` Rasmus Villemoes
2022-06-20  0:42 ` [PATCH v4 08/34] lib/printbuf: Tabstops, indenting Kent Overstreet
2022-06-21  8:14   ` Rasmus Villemoes
2022-06-20  0:42 ` [PATCH v4 09/34] lib/printbuf: Unit specifiers Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 10/34] lib/pretty-printers: prt_string_option(), prt_bitflags() Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 11/34] vsprintf: Improve number() Kent Overstreet
2022-06-21  8:33   ` Rasmus Villemoes
2022-06-20  0:42 ` [PATCH v4 12/34] vsprintf: prt_u64_minwidth(), prt_u64() Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 13/34] test_printf: Drop requirement that sprintf not write past nul Kent Overstreet
2022-06-21  7:19   ` Rasmus Villemoes
2022-06-21  7:52     ` Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 14/34] vsprintf: Start consolidating printf_spec handling Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 15/34] vsprintf: Refactor resource_string() Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 16/34] vsprintf: Refactor fourcc_string() Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 17/34] vsprintf: Refactor ip_addr_string() Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 18/34] vsprintf: Refactor mac_address_string() Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 19/34] vsprintf: time_and_date() no longer takes printf_spec Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 20/34] vsprintf: flags_string() " Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 21/34] vsprintf: Refactor device_node_string, fwnode_string Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 22/34] vsprintf: Refactor hex_string, bitmap_string_list, bitmap_string Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 23/34] Input/joystick/analog: Convert from seq_buf -> printbuf Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 24/34] mm/memcontrol.c: Convert to printbuf Kent Overstreet
2022-06-20 11:37   ` Michal Hocko
2022-06-20 15:13     ` Kent Overstreet
2022-06-20 15:52       ` Michal Hocko
2022-06-20  0:42 ` [PATCH v4 25/34] clk: tegra: bpmp: " Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 26/34] tools/testing/nvdimm: " Kent Overstreet
2022-06-24 19:32   ` Dan Williams
2022-06-24 23:42     ` Santosh Sivaraj
2022-07-01  6:32       ` Shivaprasad G Bhat
2022-06-20  0:42 ` [PATCH v4 27/34] powerpc: " Kent Overstreet
2022-06-20  0:42   ` Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 28/34] x86/resctrl: " Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 29/34] PCI/P2PDMA: " Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 30/34] tracing: trace_events_synth: " Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 31/34] d_path: prt_path() Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 32/34] ACPI/APEI: Add missing include Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 33/34] tracing: Convert to printbuf Kent Overstreet
2022-06-20  0:42 ` [PATCH v4 34/34] Delete seq_buf Kent Overstreet
2022-06-20  4:19 ` [PATCH v4 00/34] Printbufs - new data structure for building strings David Laight
2022-06-20  4:54   ` Matthew Wilcox
2022-06-20  8:00     ` David Laight
2022-06-20 15:07   ` Kent Overstreet
2022-06-20 15:21     ` David Laight
2022-06-21  0:38     ` Joe Perches
2022-06-21  0:57       ` Kent Overstreet
2022-06-21  1:26         ` Joe Perches
2022-06-21  2:10           ` Joe Perches
2022-06-26 19:53             ` [RFC[ Alloc in vsprintf Joe Perches
2022-06-26 20:06               ` Kent Overstreet
2022-06-26 20:13                 ` Joe Perches
2022-06-26 20:19               ` Linus Torvalds
2022-06-26 20:39                 ` Joe Perches [this message]
2022-06-26 20:51                   ` Kent Overstreet
2022-06-26 21:02                     ` Joe Perches
2022-06-26 21:10                       ` Kent Overstreet
2022-06-26 20:54                   ` Linus Torvalds
2022-06-27  8:25                 ` David Laight
2022-06-28  2:56                   ` Kent Overstreet
2022-06-21  2:31           ` [PATCH v4 00/34] Printbufs - new data structure for building strings Kent Overstreet
2022-06-21  3:11   ` Kent Overstreet
2022-06-21  6:11 ` Rasmus Villemoes
2022-06-21  8:01   ` Kent Overstreet
2022-07-19 23:15 ` Steven Rostedt
2022-07-19 23:43   ` Kent Overstreet
2022-07-20  0:05     ` Steven Rostedt
2022-07-20  0:17       ` Kent Overstreet
2022-07-20  1:11         ` Steven Rostedt
2022-07-20  1:31           ` Kent Overstreet
2022-07-20  1:37             ` Steven Rostedt

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