From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Eugene Surovegin <ebs@ebshome.net>
Cc: Paul Mackerras <paulus@samba.org>, linuxppc-dev@lists.linuxppc.org
Subject: Re: set_rtc_time() cleanup / normalization
Date: 14 May 2003 10:32:33 +0200 [thread overview]
Message-ID: <1052901153.664.15.camel@gaston> (raw)
In-Reply-To: <5.1.0.14.2.20030513161846.03805338@mail.ebshome.net>
>
> 2) set_rtc_time() implementation for concrete RTC device *maybe* slow or
> just cannot
> be called from the interrupt context.
> Why just don't fix actual RTC code in each case ?
> It may be useful to provide some *generic* facility for such cases.
It may just not be fixable cleanly. If you RTC is on a bus which requires
some semaphoring for access (i2c does on pmac, though so far, the RTC isn't
on i2c on these, I admit), or which is just so slow that you really do NOT
want to block the machine in an interrupt that long ?
Actually, the later is the most nasty. Also, since set_rtc_time() is used for
both interrupt call and non-interrupt call, it cannot make assumptions about
beeing able to schedule or not, thus causing the same latency problem when
called via /dev/rtc, possibly a good DOS attack tool, but more simply, it
just suck that way...
Ben.
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2003-05-14 8:32 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-12 21:17 set_rtc_time() cleanup / normalization Wolfgang Denk
2003-05-13 0:16 ` Dan Malek
2003-05-13 7:52 ` Geert Uytterhoeven
2003-05-13 8:18 ` Gabriel Paubert
[not found] ` <Pine.GSO.4.21.0305131051420.20323-100000@vervain.sonytel.be>
2003-05-13 10:21 ` Gabriel Paubert
2003-05-13 13:35 ` Wolfgang Denk
2003-05-13 12:03 ` Richard Zidlicky
2003-05-13 23:05 ` Paul Mackerras
2003-05-13 23:33 ` Eugene Surovegin
2003-05-14 0:08 ` Wolfgang Denk
[not found] ` <5.1.0.14.2.20030513171616.037f6800@mail.ebshome.net>
2003-05-14 3:47 ` Matt Porter
[not found] ` <5.1.0.14.2.20030513214040.02a6e6d0@mail.ebshome.net>
[not found] ` <3EC1DB1F.8000408@embeddededge.com>
2003-05-14 6:41 ` Eugene Surovegin
2003-05-14 6:47 ` Wolfgang Denk
2003-05-14 8:32 ` Benjamin Herrenschmidt [this message]
2003-05-14 15:57 ` Gabriel Paubert
2003-05-14 16:41 ` Eugene Surovegin
2003-05-14 15:50 ` Gabriel Paubert
2003-05-14 15:43 ` Gabriel Paubert
2003-05-14 16:28 ` Dan Malek
2003-05-15 18:04 ` Gabriel Paubert
2003-05-15 18:21 ` Wolfgang Denk
[not found] ` <20030515184412.GA22327@iram.es>
2003-05-15 19:37 ` Benjamin Herrenschmidt
[not found] <20030514230638.GB1687@linux-m68k.org>
[not found] ` <Pine.GSO.4.21.0305151031410.13683-100000@vervain.sonytel.be>
2003-05-15 10:45 ` Gabriel Paubert
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