/** * lib/minmax.c: windowed min/max tracker * * Kathleen Nichols' algorithm for tracking the minimum (or maximum) * value of a data stream over some fixed time interval. (E.g., * the minimum RTT over the past five minutes.) It uses constant * space and constant time per update yet almost always delivers * the same minimum as an implementation that has to keep all the * data in the window. * * The algorithm keeps track of the best, 2nd best & 3rd best min * values, maintaining an invariant that the measurement time of * the n'th best >= n-1'th best. It also makes sure that the three * values are widely separated in the time window since that bounds * the worse case error when that data is monotonically increasing * over the window. * * Upon getting a new min, we can forget everything earlier because * it has no value - the new min is <= everything else in the window * by definition and it's the most recent. So we restart fresh on * every new min and overwrites 2nd & 3rd choices. The same property * holds for 2nd & 3rd best. */ #include #include /* As time advances, update the 1st, 2nd, and 3rd choices. */ static u32 minmax_subwin_update(struct minmax *m, u32 win, const struct minmax_sample *val) { u32 dt = val->t - m->s[0].t; if (unlikely(dt > win)) { /* * Passed entire window without a new val so make 2nd * choice the new val & 3rd choice the new 2nd choice. * we may have to iterate this since our 2nd choice * may also be outside the window (we checked on entry * that the third choice was in the window). */ m->s[0] = m->s[1]; m->s[1] = m->s[2]; m->s[2] = *val; if (unlikely(val->t - m->s[0].t > win)) { m->s[0] = m->s[1]; m->s[1] = m->s[2]; m->s[2] = *val; } } else if (unlikely(m->s[1].t == m->s[0].t) && dt > win/4) { /* * We've passed a quarter of the window without a new val * so take a 2nd choice from the 2nd quarter of the window. */ m->s[2] = m->s[1] = *val; } else if (unlikely(m->s[2].t == m->s[1].t) && dt > win/2) { /* * We've passed half the window without finding a new val * so take a 3rd choice from the last half of the window */ m->s[2] = *val; } return m->s[0].v; } /* Check if new measurement updates the 1st, 2nd or 3rd choice max. */ u32 minmax_running_max(struct minmax *m, u32 win, u32 t, u32 meas) { struct minmax_sample val = { .t = t, .v = meas }; if (unlikely(val.v >= m->s[0].v) || /* found new max? */ unlikely(val.t - m->s[2].t > win)) /* nothing left in window? */ return minmax_reset(m, t, meas); /* forget earlier samples */ if (unlikely(val.v >= m->s[1].v)) m->s[2] = m->s[1] = val; else if (unlikely(val.v >= m->s[2].v)) m->s[2] = val; return minmax_subwin_update(m, win, &val); } EXPORT_SYMBOL(minmax_running_max); /* Check if new measurement updates the 1st, 2nd or 3rd choice min. */ u32 minmax_running_min(struct minmax *m, u32 win, u32 t, u32 meas) { struct minmax_sample val = { .t = t, .v = meas }; if (unlikely(val.v <= m->s[0].v) || /* found new min? */ unlikely(val.t - m->s[2].t > win)) /* nothing left in window? */ return minmax_reset(m, t, meas); /* forget earlier samples */ if (unlikely(val.v <= m->s[1].v)) m->s[2] = m->s[1] = val; else if (unlikely(val.v <= m->s[2].v)) m->s[2] = val; return minmax_subwin_update(m, win, &val); } 89f686725ff5bc3b9b25'>pxa/magician.c
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authorThomas Gleixner <tglx@linutronix.de>2017-01-31 09:37:34 +0100
committerThomas Gleixner <tglx@linutronix.de>2017-01-31 21:47:58 +0100
commit0becc0ae5b42828785b589f686725ff5bc3b9b25 (patch)
treebe6d0e1f37c38ed0a7dd5da2d4b1e93f0fb43101 /sound/soc/pxa/magician.c
parent24c2503255d35c269b67162c397a1a1c1e02f6ce (diff)
x86/mce: Make timer handling more robust
Erik reported that on a preproduction hardware a CMCI storm triggers the BUG_ON in add_timer_on(). The reason is that the per CPU MCE timer is started by the CMCI logic before the MCE CPU hotplug callback starts the timer with add_timer_on(). So the timer is already queued which triggers the BUG. Using add_timer_on() is pretty pointless in this code because the timer is strictlty per CPU, initialized as pinned and all operations which arm the timer happen on the CPU to which the timer belongs. Simplify the whole machinery by using mod_timer() instead of add_timer_on() which avoids the problem because mod_timer() can handle already queued timers. Use __start_timer() everywhere so the earliest armed expiry time is preserved. Reported-by: Erik Veijola <erik.veijola@intel.com> Tested-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Borislav Petkov <bp@alien8.de> Cc: Tony Luck <tony.luck@intel.com> Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1701310936080.3457@nanos Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'sound/soc/pxa/magician.c')