Re: [v1][PATCH 3/6] book3e/kgdb: update thread's dbcr0

[tiejun.chen]

On 12/21/2012 02:41 AM, Kumar Gala wrote:
> On Dec 20, 2012, at 3:08 AM, Tiejun Chen wrote:
>
> > gdb always need to generate a single step properly to invoke
> > a kgdb state. But with lazy interrupt, book3e can't always
> > trigger a debug exception with a single step since the current
> > is blocked for handling those pending exception, then we miss
> > that expected dbcr configuration at last to generate a debug
> > exception.
> >
> > So here we also update thread's dbcr0 to make sure the current
> > can go back with that missed dbcr0 configuration.
> >
> > Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxxxxxx>
> > ---
> > arch/powerpc/kernel/kgdb.c |   10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
> > index c470a40..516b44b 100644
> > --- a/arch/powerpc/kernel/kgdb.c
> > +++ b/arch/powerpc/kernel/kgdb.c
> > @@ -426,8 +426,18 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
> > 		/* set the trace bit if we're stepping */
> > 		if (remcom_in_buffer[0] == 's') {
> > #ifdef CONFIG_PPC_ADV_DEBUG_REGS
> > +#ifdef CONFIG_PPC_BOOK3E
>
> Should this really be CONFIG_PPC64 or CONFIG_PPC_BOOK3E_64?

Yes, I think CONFIG_PPC_BOOK3E_64 is better currently. Because I didn't validate 
this on power arch since I have no a real machine :)

> > +			/* With lazy interrut we have to update thread dbcr0 here
> > +			 * to make sure we can set debug properly at last to invoke
> > +			 * kgdb again to work well.
> > +			 */
> > +			current->thread.dbcr0 =
> > +				mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM;
> > +			mtspr(SPRN_DBCR0, current->thread.dbcr0);
> > +#else
> > 			mtspr(SPRN_DBCR0,
> > 			      mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
> > +#endif
>
> Can we code this so we don't need the #else?

I guess you're saying something like this:

---
diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index c470a40..b2df42a 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -409,7 +409,7 @@ int kgdb_arch_handle_exception(int vector, int signo, int 
err_code,
 			       struct pt_regs *linux_regs)
 {
 	char *ptr = &remcom_in_buffer[1];
-	unsigned long addr;
+	unsigned long addr, dbcr0;

 	switch (remcom_in_buffer[0]) {
 		/*
@@ -426,8 +426,15 @@ int kgdb_arch_handle_exception(int vector, int signo, int 
err_code,
 		/* set the trace bit if we're stepping */
 		if (remcom_in_buffer[0] == 's') {
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
-			mtspr(SPRN_DBCR0,
-			      mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
+			dbcr0 = mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM;
+			mtspr(SPRN_DBCR0, dbcr0);
+#ifdef CONFIG_PPC_BOOK3E_64
+			/* With lazy interrut we have to update thread dbcr0 here
+			 * to make sure we can set debug properly at last to invoke
+			 * kgdb again to work well.
+			 */
+			current->thread.dbcr0 = dbcr0;
+#endif
 			linux_regs->msr |= MSR_DE;
 #else
 			linux_regs->msr |= MSR_SE;
--
1.7.9.5

Tiejun
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