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

Tiejun Chen tiejun.chen at windriver.com
Thu Dec 20 20:08:27 EST 2012

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

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 at windriver.com>
 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') {
+			/* 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);
 			      mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
 			linux_regs->msr |= MSR_DE;
 			linux_regs->msr |= MSR_SE;

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