📄 soft_irqs.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html><head> <title></title> <link rel="stylesheet" media="screen" type="text/css" href="./style.css" /> <link rel="stylesheet" media="screen" type="text/css" href="./design.css" /> <link rel="stylesheet" media="print" type="text/css" href="./print.css" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /></head><body><a href=start.html>start</a></br><h2><a name="soft_irqs" id="soft_irqs">Soft Irqs</a></h2><div class="level2"><p> First a review of some system services. These are deferred processing entities that can take over compute intensive or process intensive tasks from fast running interrupt routines.</p><ul><li class="level1"><div class="li"> Bottom halves. These are serialized globally so that only one can execute on ANY cpu at one time.</div></li></ul><ul><li class="level1"><div class="li"> Tasklets. These are serialized per CPU so that a given tasklet will run to completion before being executed again.</div></li></ul><ul><li class="level1"><div class="li"> Soft Irqs. Unlike bottom halfs and tasklets, soft irqs can be serviced at any time by any available CPU.</div></li></ul><p>They are mainly used in network drivers where each packet must be serviced as fast as possible by any CPU available</p><p> The soft irq routine must be written so thet it permits this sort of operation. It must be reentrant.</p><p>The core kernel code is in <strong>linux-2.6.x/kernel/softirq.c</strong>.</p><p> The main kernel timer is another example of a well used soft Irq linux-2.6.x/kernel/timer.c </p><pre class="code c"> <span class="kw4">void</span> run_local_timers<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span><span class="br0">{</span> raise_softirq<span class="br0">(</span>TIMER_SOFTIRQ<span class="br0">)</span>;<span class="br0">}</span> <span class="kw4">void</span> __init init_timers<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span><span class="br0">{</span> timer_cpu_notify<span class="br0">(</span>&timers_nb, <span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">long</span><span class="br0">)</span>CPU_UP_PREPARE, <span class="br0">(</span><span class="kw4">void</span> *<span class="br0">)</span><span class="br0">(</span><span class="kw4">long</span><span class="br0">)</span>smp_processor_id<span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>; register_cpu_notifier<span class="br0">(</span>&timers_nb<span class="br0">)</span>; open_softirq<span class="br0">(</span>TIMER_SOFTIRQ, run_timer_softirq, <span class="kw2">NULL</span><span class="br0">)</span>;<span class="br0">}</span> </pre><p>The system softirqs are defined in the file <strong>linux-2.6.x/include/linux/interrupt.h</strong></p><p> enum {</p><pre class="code"> HI_SOFTIRQ=0, TIMER_SOFTIRQ, NET_TX_SOFTIRQ, NET_RX_SOFTIRQ, SCSI_SOFTIRQ, TASKLET_SOFTIRQ</pre><p>};</p></div></body></html>⌨️ 快捷键说明
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