From: Scott Wood Date: Mon, 13 May 2013 14:14:53 +0000 (+0000) Subject: powerpc/booke64: Fix kernel hangs at kernel_dbg_exc X-Git-Tag: v3.10-rc2~31^2~9 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6cecf76b47ba6bea3c81d170afc2e0b244e5849c;p=pandora-kernel.git powerpc/booke64: Fix kernel hangs at kernel_dbg_exc MSR_DE is not cleared on entry to the kernel, and we don't clear it explicitly outside of debug code. If we have MSR_DE set in prime_debug_regs(), and the new thread has events enabled in DBCR0 (e.g. ICMP is set in thread->dbsr0, even though it was cleared in the real DBCR0 when the thread got scheduled out), we'll end up taking a debug exception in the kernel when DBCR0 is loaded. DSRR0 will not point to an exception vector, and the kernel ends up hanging at kernel_dbg_exc. Fix this by always clearing MSR_DE when we load new debug state. Another observed source of kernel_dbg_exc hangs is with the branch taken event. If this event is active, but we take a non-debug trap (e.g. a TLB miss or an asynchronous interrupt) before the next branch. We end up taking a branch-taken debug exception on the initial branch instruction of the exception vector, but because the debug exception is DBSR_BT rather than DBSR_IC we branch to kernel_dbg_exc before even checking the DSRR0 address. Fix this by checking for DBSR_BT as well as DBSR_IC, which is what 32-bit does and what the comments suggest was intended in the 64-bit code as well. Signed-off-by: Scott Wood Signed-off-by: Benjamin Herrenschmidt --- Reading git-diff-tree failed