Messages in this thread | | | From | "Elliott, Robert (Server Storage)" <> | Subject | RE: [PATCH RESEND v8] iopoll: Introduce memory-mapped IO polling macros | Date | Tue, 25 Nov 2014 00:53:19 +0000 |
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> -----Original Message----- > From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel- > owner@vger.kernel.org] On Behalf Of Mitchel Humpherys > Sent: Monday, 24 November, 2014 2:15 PM ... > From: Matt Wagantall <mattw@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
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