On Mon, May 24, 2010 at 08:19:21AM +0100, Russell King - ARM Linux wrote: > On Mon, May 24, 2010 at 11:23:55AM +0800, Ming Lei wrote: > > On Sun, 23 May 2010 20:47:46 +0100 > > Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > > > Moreover, I put to you that it's utterly pointless - and a waste of > > > CPU time - telling lockdep about the IRQ masking when an exception > > > > Yes, the patch still tries to remove the pointless trace of IRQ masking, > > such as: replace disable_irq with disable_irq_notrace. > > > > > occurs, and it's also pointless telling lockdep about the IRQ > > > unmasking when we resume userspace. > > > > Even it is pointless, but if lockdep doesn't see the IRQ unmasking, the > > warning "unannotated irqs-on" will be triggered and lockdep doe not work > > any longer, so we have to remove the warning to make lockdep workable on > > ARM, could you agree on it? It is the main purpose of the patch. > > I'm sorry, I think we have a communication issue; you're not understanding > the points that I'm making. I feel I'm wasting my time trying to explain > it. > > I'm not merging your patch as-is because I believe it to be wrong. Right, I see what the problem is now - it's all to do with threads created with kernel_thread() confusing lockdep. I'm of the opinion that all your changes in entry*.S are the wrong way to fix this - not only does it add additional overhead where none is really necessary, it adds additional complexity. So, here's a patch to solve the warning you quoted. diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index acf5e6f..a5f8fd0 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -351,17 +351,25 @@ EXPORT_SYMBOL(dump_fpu); /* * Shuffle the argument into the correct register before calling the - * thread function. r1 is the thread argument, r2 is the pointer to - * the thread function, and r3 points to the exit function. + * thread function. r4 is the thread argument, r5 is the pointer to + * the thread function, and r6 points to the exit function. */ extern void kernel_thread_helper(void); asm( ".pushsection .text\n" " .align\n" " .type kernel_thread_helper, #function\n" "kernel_thread_helper:\n" -" mov r0, r1\n" -" mov lr, r3\n" -" mov pc, r2\n" +#ifdef CONFIG_TRACE_IRQFLAGS +" bl trace_hardirqs_on\n" +#endif +#if __LINUX_ARM_ARCH__ >= 6 +" cpsie i\n" +#else +" msr cpsr_c, r7\n" +#endif +" mov r0, r4\n" +" mov lr, r6\n" +" mov pc, r5\n" " .size kernel_thread_helper, . - kernel_thread_helper\n" " .popsection"); @@ -391,11 +399,12 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) memset(®s, 0, sizeof(regs)); - regs.ARM_r1 = (unsigned long)arg; - regs.ARM_r2 = (unsigned long)fn; - regs.ARM_r3 = (unsigned long)kernel_thread_exit; + regs.ARM_r4 = (unsigned long)arg; + regs.ARM_r5 = (unsigned long)fn; + regs.ARM_r6 = (unsigned long)kernel_thread_exit; + regs.ARM_r7 = SVC_MODE | PSR_ISETSTATE; regs.ARM_pc = (unsigned long)kernel_thread_helper; - regs.ARM_cpsr = SVC_MODE | PSR_ENDSTATE | PSR_ISETSTATE; + regs.ARM_cpsr = SVC_MODE | PSR_ENDSTATE | PSR_ISETSTATE | PSR_I_BIT; return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, ®s, 0, NULL, NULL); } -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
