From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 1A516DDE46 for ; Fri, 26 Oct 2007 11:51:07 +1000 (EST) Subject: Re: Apparent kernel bug with GDB on ppc405 From: Benjamin Herrenschmidt To: Grant Likely In-Reply-To: References: <20071024194640.GB19691@waste.org> <20071024204215.GC19691@waste.org> <20071024215421.GF19691@waste.org> <20071024223250.GI19691@waste.org> Content-Type: text/plain Date: Fri, 26 Oct 2007 11:50:53 +1000 Message-Id: <1193363453.7018.38.camel@pasglop> Mime-Version: 1.0 Cc: gdb@sourceware.org, linuxppc-embedded@ozlabs.org, Matt Mackall Reply-To: benh@kernel.crashing.org List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2007-10-24 at 16:40 -0600, Grant Likely wrote: > On 10/24/07, Grant Likely wrote: > > > Not completely implausible, but a) why isn't this seen on basically > > > every machine with software TLB? b) why does -local- GDB, which is > > > presumably doing much less work than gdbserver + network stack, not fail? > > > > a) I don't know.... very odd. > > > > b) gdb is big. It probably touches far more pages (via library calls) > > than gdbserver. The network stack is also big, but it's probably more > > localized too. > > > > Niceing down the host also makes sense because if the PC is being slow > > then the target may go off and run other things while between setting > > the breakpoint and getting the 'go' command. > > > > Can you grab a snapshot of the TLB before and after setting the breakpoint? > > Or; probably more relevant, before and after the page copy? COW does ptep_clear_flush before setting the new TLB which does a flush_tlb_page() so that should work. Ben.