Matt Mackall wrote: > On Wed, 2008-01-16 at 10:00 +0900, Tejun Heo wrote: >> And mprintk the following. >> >> code: >> DEFINE_MPRINTK(mp, 2 * 80); >> >> mprintk_set_header(&mp, KERN_INFO "ata%u.%2u: ", 1, 0); >> mprintk_push(&mp, "ATA %d", 7); >> mprintk_push(&mp, ", %u sectors\n", 1024); >> mprintk(&mp, "everything seems dandy\n"); > > I prefer Matthew Wilcox's stringbuf approach which does proper memory > management and isn't specific to printk: > > http://www.ussg.iu.edu/hypermail/linux/kernel/0710.3/0517.html
Yeap, that's generic and nice but I think both 'generic' and 'proper memory management' are weakness if what you're trying to do is to support collecting messages in pieces and putting it out via printk. Please consider the following scenario. You're in an interrupt handler and detected a severe error condition which should be notified to the user but the information is rather complex and best built in pieces, so you create a stringbuf and does sb_printf() to it w/ GFP_ATOMIC but alas memory allocation failed and you end up printing "out of memory" unless you detect the failure and go back and printk messages piece-by-piece manually. I would rather assemble the message manually from the get-go into an on-stack buffer. By being specifially 'printk' and let the user supply buffer, which in most cases can be on-stack (messages shouldn't be too long anyway), mprintk either can avoid those problems from the beginning or can automatically work around when problem arises (initialized with NULL buffer from allocation failure) without losing any message, so it's essentially as simple as using printk. There is no error handling (both mprintk and kfree can handle NULL pointer) and the message is guaranteed to go out no matter what. Auto-expanding string buffer is nice but I don't think it fits the bill here. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
