> -----Original Message----- > From: linux-kernel-ow...@vger.kernel.org [mailto:linux-kernel- > ow...@vger.kernel.org] On Behalf Of Mitchel Humpherys > Sent: Monday, 24 November, 2014 2:15 PM ... > From: Matt Wagantall <ma...@codeaurora.org> > > It is sometimes necessary to poll a memory-mapped register until its value > satisfies some condition. Introduce a family of convenience macros that do > this. Tight-looping, sleeping, and timing out can all be accomplished > using these macros. > ... > +#define readx_poll_timeout(op, addr, val, cond, sleep_us, timeout_us) > \ > +({ \ > + ktime_t timeout = ktime_add_us(ktime_get(), timeout_us); \ > + might_sleep_if(sleep_us); \ > + for (;;) { \ > + (val) = op(addr); \ > + if (cond) \ > + break; \ > + if (timeout_us && ktime_compare(ktime_get(), timeout) > 0) { > \ > + (val) = op(addr); \ > + break; \ > + } \ > + if (sleep_us) \ > + usleep_range((sleep_us >> 2) + 1, sleep_us); \
The hpsa SCSI driver used to use usleep_range in a loop like that, but we found that it caused scheduler problems during boots because it uses TASK_UNINTERRUPTIBLE: [ 9.260668] [sched_delayed] sched: RT throttling activated msleep() worked much better. --- Rob Elliott HP Server Storage -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
