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From: Alan Stern <stern@rowland.harvard.edu>
To: Borislav Petkov <bp@alien8.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
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Subject: Re: [PATCH v0 42/42] notifier: Return an error when callback is already registered
Date: Mon, 8 Nov 2021 15:59:26 -0500	[thread overview]
Message-ID: <20211108205926.GA1678880@rowland.harvard.edu> (raw)
In-Reply-To: <YYlOmd0AeA8DSluD@zn.tnic>

On Mon, Nov 08, 2021 at 05:21:45PM +0100, Borislav Petkov wrote:
> On Mon, Nov 08, 2021 at 05:12:16PM +0100, Geert Uytterhoeven wrote:
> > Returning void is the other extreme ;-)
> > 
> > There are 3 levels (ignoring BUG_ON()/panic () inside the callee):
> >   1. Return void: no one can check success or failure,
> >   2. Return an error code: up to the caller to decide,
> >   3. Return a __must_check error code: every caller must check.
> > 
> > I'm in favor of 2, as there are several places where it cannot fail.
> 
> Makes sense to me. I'll do that in the next iteration.

Is there really any reason for returning an error code?  For example, is 
it anticipated that at some point in the future these registration calls 
might fail?

Currently, the only reason for failing to register a notifier callback 
is because the callback is already registered.  In a sense this isn't 
even an actual failure -- after the registration returns the callback 
_will_ still be registered.

So if the call can never really fail, why bother with a return code?  
Especially since the caller can't do anything with such a code value.

Given the current state of affairs, I vote in favor of 1 (plus a WARN or 
something similar to generate a stack dump in the callee, since double 
registration really is a bug).

Alan Stern

  reply	other threads:[~2021-11-08 20:59 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-08 10:11 [PATCH v0 00/42] notifiers: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 01/42] x86: Check notifier registration return value Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 02/42] xen/x86: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 03/42] impi: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 04/42] clk: renesas: " Borislav Petkov
2021-11-08 14:12   ` Geert Uytterhoeven
2021-11-08 10:11 ` [PATCH v0 05/42] dca: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 06/42] firmware: " Borislav Petkov
2021-11-12 18:43   ` Cristian Marussi
2021-11-08 10:11 ` [PATCH v0 07/42] drm/i915: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 08/42] Drivers: hv: vmbus: " Borislav Petkov
2021-11-08 11:16   ` Wei Liu
2021-11-08 11:39     ` Borislav Petkov
2021-11-08 11:45       ` Wei Liu
2021-11-08 12:08         ` Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 09/42] iio: proximity: cros_ec: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 10/42] leds: trigger: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 11/42] misc: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 12/42] ethernet: chelsio: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 13/42] power: reset: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 14/42] remoteproc: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 15/42] scsi: target: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 16/42] USB: " Borislav Petkov
2021-11-08 14:05   ` Alan Stern
2021-11-08 14:09     ` Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 17/42] drivers: video: " Borislav Petkov
2021-11-08 11:16   ` Wei Liu
2021-11-08 10:11 ` [PATCH v0 18/42] drivers/xen: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 19/42] kernel/hung_task: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 20/42] rcu: " Borislav Petkov
2021-11-08 16:53   ` Paul E. McKenney
2021-11-08 10:11 ` [PATCH v0 21/42] tracing: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 22/42] net: fib_notifier: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 23/42] ASoC: soc-jack: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 24/42] staging: olpc_dcon: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 25/42] arch/um: " Borislav Petkov
2021-11-08 10:23   ` Johannes Berg
2021-11-08 10:48     ` Borislav Petkov
2021-11-08 10:56       ` Johannes Berg
2021-11-08 10:11 ` [PATCH v0 26/42] alpha: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 27/42] bus: brcmstb_gisb: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 28/42] soc: bcm: brcmstb: pm: pm-arm: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 29/42] arm64: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 30/42] soc/tegra: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 31/42] parisc: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 32/42] macintosh/adb: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 33/42] mips: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 34/42] powerpc: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 35/42] sh: " Borislav Petkov
2021-11-08 13:31   ` Geert Uytterhoeven
2021-11-08 13:49     ` Borislav Petkov
2021-11-08 14:03       ` Geert Uytterhoeven
2021-11-08 14:48   ` Sergey Shtylyov
2021-11-08 10:11 ` [PATCH v0 36/42] s390: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 37/42] sparc: " Borislav Petkov
2021-11-08 19:59   ` David Miller
2021-11-08 10:11 ` [PATCH v0 38/42] xtensa: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 39/42] crypto: ccree - check " Borislav Petkov
2021-11-12 18:32   ` Cristian Marussi
2021-11-12 18:48     ` Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 40/42] EDAC/altera: Check " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 41/42] power: supply: ab8500: " Borislav Petkov
2021-11-08 10:11 ` [PATCH v0 42/42] notifier: Return an error when callback is already registered Borislav Petkov
2021-11-08 14:07   ` Geert Uytterhoeven
2021-11-08 14:21     ` Borislav Petkov
2021-11-08 15:25       ` Geert Uytterhoeven
2021-11-08 15:58         ` Borislav Petkov
2021-11-08 16:12           ` Geert Uytterhoeven
2021-11-08 16:21             ` Borislav Petkov
2021-11-08 20:59               ` Alan Stern [this message]
2021-11-08 21:18                 ` Borislav Petkov
2021-11-08 10:19 ` [PATCH v0 00/42] notifiers: " Borislav Petkov
2021-11-08 14:17   ` Alan Stern
2021-11-08 14:24     ` Borislav Petkov
2021-11-08 14:35       ` Borislav Petkov
2021-11-08 16:23         ` Steven Rostedt
2021-11-08 16:29           ` Borislav Petkov

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