Date: Wed, 02 Nov 2005 12:12:48 -0700 (MST) From: Warner Losh <imp@bsdimp.com> To: dinesh@alphaque.com Cc: freebsd-hackers@freebsd.org Subject: Re: locking in a device driver Message-ID: <20051102.121248.74711520.imp@bsdimp.com> In-Reply-To: <43690424.1040904@alphaque.com> References: <4361044B.50807@alphaque.com> <20051027.205250.55834228.imp@bsdimp.com> <43690424.1040904@alphaque.com>
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From: Dinesh Nair <dinesh@alphaque.com> Subject: Re: locking in a device driver Date: Thu, 03 Nov 2005 02:23:32 +0800 > > > On 10/28/05 10:52 M. Warner Losh said the following: > > libc_r will block all other threads in the application while an ioctl > > executes. libpthread and libthr won't. I've had several bugs at work > > so if the userland thread does an ioctl, and the the driver goes to > tsleep() when the ioctl is received, all other threads are also blocked > from executing, i.e wont be context switched to run ? Yes. if you tsleep with signals enabled, the periodic timer will go off, and you'll return early. This typically isn't what you want either. > is this behaviour only 4.x specific or is it also there in 5.x ? This behavior is libc_r specific. Any userland threadding library will have these issues. It is fundamental to how userland threadding works. If you use libc_r on 5, you'll see exactly this behavior. If you use libpthread or libthr, you won't. Warner
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