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Last Lab

CSCI 156. Last Lab. Project 5. Not nearly as easy as it looks (esp. part B) A small problem can require reboot Backup your source! Plan extensively: not just write, test, write, test Cannot just use a while loop, as stated in proj. description

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Last Lab

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  1. CSCI 156 Last Lab

  2. Project 5 • Not nearly as easy as it looks (esp. part B) • A small problem can require reboot • Backup your source! • Plan extensively: not just write, test, write, test • Cannot just use a while loop, as stated in proj. description • Must use a wait-queue and kernel functions to manage it: • 2 queues: 1 for processes waiting to write, 1 waiting to read • 2 static globals: 1 “okToRead”, 1 “okToWrite” • 1 static global: currentBufLen • When using cat, it will call “read” until “read” returns 0

  3. Project 5 int i, is_sig; while (Already_Open) { is_sig = 0; wait_event_interruptible(WaitQ, !Already_Open); for (i = 0; i < _NSIG_WORDS && !is_sig; i++) { is_sig = current->pending.signal.sig[i] & ~current->blocked.sig[i]; } if (is_sig) { module_put(THIS_MODULE); return -EINTR; } }

  4. Project 5 //global, at the top: DECLARE_WAIT_QUEUE_HEAD(WaitQ); //in a function: wake_up(&WaitQ);

  5. Quiz! • Oh, how underhanded of me.

  6. Overview • What did we learn? • Linux filesystem: navigation, structure • C programming language: memory allocation, structures, networking, input routines, IPC • Multiple Processes, Multiple Threads • Security: Buffer Overflows • Linux kernel: configuring, building, module creation, device driver

  7. Beer • Beer quotes: • "Beer is proof that God loves us and wants us to be happy.“ - Benjamin Franklin • "He was a wise man who invented beer.“ – Plato • "All right, brain, I don't like you and you don't like me - so let's just do this and I'll get back to killing you with beer.“ - Homer Simpson • "Give me a woman who loves beer and I will conquer the world.“ - Kaiser Welhelm • "24 hours in a day, 24 beers in a case. Coincidence? I think not.“ - Paul Newman • “Without question, the greatest invention in the history of mankind is beer. Oh, I grant you the wheel was also a fine invention, but the wheel does not go nearly as well with pizza.” - Dave Barry

  8. Brewing Process • Malt the grains (done by malting company, not brewer) • Mill the grains (crush them so water can get in) • Mash and sparge the grains to extract the wort • Boil the wort (60 minutes+), add hops during • Chill the boiled wort to ~65-75 degrees • Add yeast, ferment for 1-2 weeks • Add priming sugar, bottle, wait 1-2 weeks to carbonate • Enjoy!

  9. Mashing • Used in all-grain brewing (as opposed to extract) • Mix grist (milled/crushed grains) with hot water • Tricks the grains into converting starch to sugar • Breaks down proteins: less haze • Different mash methods • Infusion: single temperature (145-158), rest for 1-2 hours • Step: several “steps” of increasing temp to get enzyme action • Decoction: old-world style, has steps by removing and boiling • Infusion is easy and quick, Step and Decoction are slower and harder, but give better starch conversion rates (enzymes’ optimal temperature). Decoction better for some darker styles: gives deeper color, richer caramel flavor.

  10. Sparging • Rinsing the draff (spent grains) to extract all residual sugars • Wort becomes clearer, less cloudy, more concentrated

  11. The Boil • Has many functions: • Destroy enzymes in the wort • Sterilize the wort • Allows bad chemical compounds to precipitate (DiMethylSulfide) • Hop flavor and aroma are extracted • Concentrates the wort by reducing volume • Clarfiy the wort by coagulating proteins

  12. Hops • In the past, many herbs were used to help preserve beer: hops became the eventual standard. In large amounts, was used to preserve beer to be sent to English troops in India (IPA). • Only the female plant is used: cones/flowers of the plant contain alpha acids (humulone) that isomerize during the boil: bitter resins and aromatic oil are extracted • Noble (aromatic) – Hallertau, Saaz, Golding, Fuggle • High Alpha (bittering) – Chinook, Nugget • Whole Leaves – bulky, instable, but best for aroma • Or Pellets – smaller, keep longer • Or Extract Oil – used mainly by big breweries • AAU – units of bitterness, used in recipes

  13. Yeast • Yeast strains contribute greatly to the character of the finished beer: hundreds of choices • Ale Yeast (top-fermenting, generally best at 65-75 degrees) • Lager Yeast (bottom-fermenting, best at 40-55) • Spontaneous Fermentation (Lambic) • Many belgian breweries fiercely guard their yeast strain (Rodenbach vs De Dolle) • Advanced homebrewers often experiment with cultivating their own yeast strains or harvesting yeasts from commercial brands • Overall process: respiration, fermentation (tons o' chemistry) • Yeast + Sugar + Oxygen -> CO2 + alcohol • Need an airlock!

  14. Water • Brewing water can affect flavor, yeast health, and malt extraction • Ions in water are good (distilled water = bad), but in controlled amounts • Chlorine causes chlorophenols that give off-flavors • Many metallic ions are good for yeast health in very small amts, but can kill the yeast if too much • Get tap water analyzed, or ask municipal water supplier • Many methods to control ions: • 30 min boil – kills bacteria, removes chlorine, most carbonates, etc • Ion supplements – add salts/acids to adjust pH • Carbon filter (e.g. Brita) – removes chlorine, leaves other ions alone

  15. Styles • American Lager - piss-beer • Pilsener - light color, dry lager with pungent hoppy aroma – Saaz • Pale Ale - amber/copper color, medium bitterness, lower carbonation • IPA - higher alcohol (6+?), very bitter hop character • Oktoberfest (Marzen) - malty amber ale, around 6% alc, low hop • Weisse/Wheat - mild color, usually cloudy and moderate alc • Bock - strong german style (>6%), usually dark and malty • Doppelbock - “Double” bock, richer, maltier, and usually 8+%. -ator • Rauchbier - smoked beer (tastes bacon-y), normal alc, brownish color • Porter - English dark, but lighter body than stout, usually sweeter. ~5% • Stout - English sweet stout - ~4% alc, Irish dry stout, ~5% • Imperial Stout - dry, very high alc (8+%). Sent to Ruskies • Scotch Ale - very malty, roasted flavor, around 5-7% • Barley Wine - huge malty, fruity flavor and aroma, typically ~10% • Reinheitsgebot, German Purity Law of 1516. Barley, Hops, H20, Yeast

  16. Belgian Styles • Belgian beer is the bomb • Trappists (Westmalle, Westvleteren, Chimay, Rochefort, Orval, Achel) • Tripel - Strongest (8+%), usually pale and spicy • Dubbel - usually dark brown, 6-8%, very malty and floral • Brown/Red Ales - very sour, from Flanders, some are old/new blends • Witbier - citrusy, spicy, white belgian style • Saison - farmhouse brewing, typically spicy and a little tart • Lambic - Spontaneously fermented, sour, low bitter • Gueuze is usually a mix of old/young lambic: champagne-ish carbonation • Kriek (cherry), Framboise (raspberry), Peche (peach), Cassis (blackcurrant) • Belgian Glassware - each beer has its own distinct glass (kwak, etc) to give optimal aroma for the style (and, of course, for marketing) • Each style has own pouring guidelines, amount of head

  17. Whew • Go forth and have a good beer

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