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Date: Wed, 30 Jan 2008 11:29:59 +0100 From: michael <trimarchi@...dalf.sssup.it> To: Haavard Skinnemoen <hskinnemoen@...el.com> CC: Remy Bohmer <linux@...mer.net>, fabio@...dalf.sssup.it, Andrew Victor <linux@...im.org.za>, Chip Coldwell <coldwell@...hat.com>, Marc Pignat <marc.pignat@...s.ch>, David Brownell <david-b@...bell.net>, linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk> Subject: Re: [PATCH -mm v4 6/9] atmel_serial: Split the interrupt handler Hi > On Wed, 30 Jan 2008 00:12:23 +0100 > michael <trimarchi@...dalf.sssup.it> wrote: > > >> - Voluntary Kernel Preemption the system (crash) >> - Preemptible Kernel (crash) >> > > Ouch. I'm assuming this is with DMA disabled? > > Yes, is with DMA disabled >> /* >> * Drop the lock here since it might end up calling >> * uart_start(), which takes the lock. >> spin_unlock(&port->lock); >> */ >> tty_flip_buffer_push(port->info->tty); >> /* >> spin_lock(&port->lock); >> */ >> The same code with this comments out runs >> > > Now, _that_ is strange. I can't see anything that needs protection > across that call; in fact, I think we can lock a lot less than what we > currently do. > > I explain it bad: - with spin_lock the system seems, there is no problem with Valuntary Preeption and Preemptible Kernel - with full preemption it runs but the serial line can't be used for receiving at high bit rate (using lrz) >> Complete Preemption (Real-Time) ok but the serials is just unusable due >> to too many overruns (just using lrz) >> > > Is it worse than before? IIRC Remy mentioned something about > IRQF_NODELAY being the reason for moving all this code to softirq > context in the first place; does the interrupt handler run in hardirq > context? > > In the complete preemption yes. >> The system is stable and doesn't crash reverting this patch. >> I don't test with the thread hardirqs active. >> > > Ok. > > >> Is the kmalloc correct? >> maybe: >> data = kmalloc(ATMEL_SERIAL_RINGSIZE * sizeof(struct atmel_uart_char), >> GFP_KERNEL); >> > > I think you're right. Can you change it and see if it helps? > > I just change it because I have corruption on receiving buffer. All my test are done with this fix > I guess I didn't test it thoroughly enough with DMA > disabled...slub_debug ought to catch such things, but not until we > receive enough data to actually overflow the buffer. > > I just test it I don't have buffer overflow. I protect with a spinlock the access to the register when we sending from the tasklet. It is correct? > > Why should it be? If it should, we must move the call to tasklet_init > into atmel_startup too, and I don't really see the point. > > Ok Regards Michael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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