Date: Thu, 30 Apr 2009 18:09:59 -0700 From: Marcel Moolenaar <xcllnt@mac.com> To: Rafal Jaworowski <raj@semihalf.com> Cc: "freebsd-ppc@freebsd.org" <freebsd-ppc@freebsd.org> Subject: Re: Single stepping through atomic ops Message-ID: <9904FBD1-F01A-4E7C-9E71-6C2D544352F8@mac.com> In-Reply-To: <F9D995D9-D032-498B-B252-CCED9E1D0540@semihalf.com> References: <36D74D0F-DB5D-4B3D-8A34-2AC72A5209AF@semihalf.com> <F9D995D9-D032-498B-B252-CCED9E1D0540@semihalf.com>
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Sorry for the delay... There's an effort to import GDB 6.4 I think. What's the version of GDB that is fixed? -- Marcel On Apr 30, 2009, at 2:01 AM, Rafal Jaworowski <raj@semihalf.com> wrote: > > On 2009-04-21, at 19:57, Rafal Jaworowski wrote: > >> Hi Marcel, >> I'm writing to you primarily as the gdb maintainer :-) There's a >> problem with current gdb in base when single stepping through >> atomic sequences on PowerPC (and presumably other archs with the >> load + conditional store approach for atomic ops). The effect is a >> hang because we endlessly loop due to the [always] lost reservation >> at the time of a closing stwcx. >> >> This is a known problem with gdb and it's fixed with newer >> versions, but the patches are not applicable to our gdb due to some >> infrastructure changes. The quick fix for 6.1.1 is here: >> http://people.freebsd.org/~raj/patches/powerpc/gdb-ppc-single-step.diff >> >> It's mainly a transplant of two fixes from the gdb repository >> (1.275, 1.276, deal_with_atomic_sequence) adjusted to our older gdb >> code, but it's ugly #ifdef'ed __ppc__. In order to do it cleanly we >> would need to change the signature of the SOFTWARE_SINGLE_STEP >> method so it returns a value (this is how newer gdb works), but it >> would affect gdb for all architectures. Do you see any objections >> for growing a return value here? >> >> Another direction would be importing a newer gdb code base, and be >> able to apply the fixes directly and cleanly (if at all required), >> but am not sure if there are any plans to upgrade gdb in base? Let >> me know your comments. > > Have you got any comments to this? Should I move on and commit this > as ugly as is, or would reworking SOFTWARE_SINGLE_STEP be more > desired? Any thoughts about newer gdb versions coming to the tree? > > Rafal >
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