Messages in this thread | | | Date | Tue, 15 Apr 2008 09:21:18 +0200 | From | Heiko Carstens <> | Subject | Re: + s390-tty-prepare-for-put_char-to-return-success-fail.patch added to -mm tree |
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> * NOTE: include/linux/tty_driver.h specifies that a character should be > * ignored if there is no room in the queue. This driver implements a different > * semantic in that it will block when there is no more room left. > + * > + * FIXME: putchar can currently be called from BH and other non blocking > + * handlers so this semantic isn't a good idea. > */ > -static void > +static int > sclp_vt220_put_char(struct tty_struct *tty, unsigned char ch) > { > __sclp_vt220_write(&ch, 1, 0, 0, 1); > + return 1;
Uh, oh... the comment above used to mean "block if in schedulable context or busy wait otherwise". Figuring out which context we were in was done via in_atomic(), which was broken on !SMP anyway, so that had to go. So the last parameter for __sclp_vt220_write is now an indicator if scheduling is allowed or not (1 means yes). Somebody told me that the put_char routine will only be called from schedulable context, which now doesn't seem to be true?! For the console functions we pass indeed 0 to __sclp_vt220_write since printk may be called within any context. Is that also true for the tty put_char routine?
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