Cc-ing Tejun On (03/02/18 16:54), Petr Mladek wrote: [..] > > (Though it is not immediately obvious why.) > > It is a mistery to me. The error appears when I move any of > dump_stack_print_info() or show_regs_print_info() function > definitions from kernel/printk/printk.c to lib/dump_stack.c. > All the other changes seems unrelated. > > The thing is that we basically do not touch dump_stack() definition > by that patch. Apparently dump_stack_print_info() was in lib/dump_stack.c a long time ago, but it was deliberately moved to printk.c, when kernel gained a "generic" (dummy) dump_stack() fallback. Some archs, like blackfin, define their own dump_stack() symbol and make it global via EXPORT_SYMBOL. In case of blackfin that arch-specific dump_stack() symbol invokes a global dump_stack_print_info(). If we move dump_stack_print_info() back to lib/dump_stack.c then we link both with arch/blackfin/dumpstack.o and lib/dump_stack.o, which results in multiple definitions error. If we move dump_stack_print_info() out on libdump_stack.o, then we never link with lib/dump_stack.o ... so what are we going to do with that. a) we can drop the patch and cherry pick only the kexec part b) we can try to mark dummy lib/dump_stack() as __weak EXPORT_SYMBOL and remove EXPORT_SYMBOL from arch-specific definitions. So we will end up with EXPORT_SYMBOL dump_stack() and archs may re-define it. If some arch will accidentally mark its own dump_stack() as EXPORT_SYMBOL then there should be a linkage warning - a symbol is exported twice. Something like below. Opinions? Will this work? ========= 8< ========= From: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Subject: [PATCH] dump_stack: mark dummy dump_stack() as weak --- arch/blackfin/kernel/dumpstack.c | 1 - arch/nds32/kernel/traps.c | 2 -- lib/dump_stack.c | 4 ++-- 3 files changed, 2 insertions(+), 5 deletions(-) diff --git a/arch/blackfin/kernel/dumpstack.c b/arch/blackfin/kernel/dumpstack.c index 3c992c1f8ef2..61af017130cd 100644 --- a/arch/blackfin/kernel/dumpstack.c +++ b/arch/blackfin/kernel/dumpstack.c @@ -174,4 +174,3 @@ void dump_stack(void) show_stack(current, &stack); trace_buffer_restore(tflags); } -EXPORT_SYMBOL(dump_stack); diff --git a/arch/nds32/kernel/traps.c b/arch/nds32/kernel/traps.c index 8828b4aeb72b..455bb0787367 100644 --- a/arch/nds32/kernel/traps.c +++ b/arch/nds32/kernel/traps.c @@ -166,8 +166,6 @@ void dump_stack(void) __dump(NULL, base_reg); } -EXPORT_SYMBOL(dump_stack); - void show_stack(struct task_struct *tsk, unsigned long *sp) { unsigned long *base_reg; diff --git a/lib/dump_stack.c b/lib/dump_stack.c index 5cff72f18c4a..9cf4465dbffa 100644 --- a/lib/dump_stack.c +++ b/lib/dump_stack.c @@ -85,7 +85,7 @@ static void __dump_stack(void) #ifdef CONFIG_SMP static atomic_t dump_lock = ATOMIC_INIT(-1); -asmlinkage __visible void dump_stack(void) +asmlinkage __weak __visible void dump_stack(void) { unsigned long flags; int was_locked; @@ -118,7 +118,7 @@ asmlinkage __visible void dump_stack(void) local_irq_restore(flags); } #else -asmlinkage __visible void dump_stack(void) +asmlinkage __weak __visible void dump_stack(void) { __dump_stack(); } -- 2.16.2 -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html