Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2 powerpc] fix unpaired __trace_hcall_entry and __trace_hcall_exit | From | Li Zhong <> | Date | Sun, 08 Jan 2012 11:54:52 +0800 |
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On Tue, 2012-01-03 at 11:54 +1100, Benjamin Herrenschmidt wrote: > On Mon, 2011-12-19 at 10:06 +0800, Li Zhong wrote: > > Unpaired calling of __trace_hcall_entry and __trace_hcall_exit could > > cause incorrect preempt count. And it might happen as the global > > variable hcall_tracepoint_refcount is checked separately before calling > > them. > > > > I don't know much about the powerpc arch. But the idea here is to store > > the hcall_tracepoint_refcount locally, so __trace_hcall_entry and > > __trace_hcall_exit will be called or not called in pair by checking the > > same value. > > Can you re-use an existing spot in the stack frame rather than adding > this entry ? There's plenty of unused spots :-) For example the link > editor doubleword is never going to be used in that function, we could > hijack it safely. It would make the patch (and the code) simpler. > > Cheers, > Ben.
Hi Ben,
Thank you for the suggestion. Below is the updated version, much less code changes :) Would you please help review again to see whether my understanding is correct?
Thanks, Zhong
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- arch/powerpc/platforms/pseries/hvCall.S | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/hvCall.S b/arch/powerpc/platforms/pseries/hvCall.S index fd05fde..3ce73d0 100644 --- a/arch/powerpc/platforms/pseries/hvCall.S +++ b/arch/powerpc/platforms/pseries/hvCall.S @@ -36,6 +36,7 @@ BEGIN_FTR_SECTION; \ b 1f; \ END_FTR_SECTION(0, 1); \ ld r12,hcall_tracepoint_refcount@toc(r2); \ + std r12,32(r1); \ cmpdi r12,0; \ beq+ 1f; \ mflr r0; \ @@ -74,7 +75,7 @@ END_FTR_SECTION(0, 1); \ BEGIN_FTR_SECTION; \ b 1f; \ END_FTR_SECTION(0, 1); \ - ld r12,hcall_tracepoint_refcount@toc(r2); \ + ld r12,32(r1); \ cmpdi r12,0; \ beq+ 1f; \ mflr r0; \ -- 1.7.5.4
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