Mercurial > hg > nginx-quic
annotate src/core/ngx_spinlock.c @ 4385:70ba81827472
Cache locks initial implementation.
New directives: proxy_cache_lock on/off, proxy_cache_lock_timeout. With
proxy_cache_lock set to on, only one request will be allowed to go to
upstream for a particular cache item. Others will wait for a response
to appear in cache (or cache lock released) up to proxy_cache_lock_timeout.
Waiting requests will recheck if they have cached response ready (or are
allowed to run) every 500ms.
Note: we intentionally don't intercept NGX_DECLINED possibly returned by
ngx_http_file_cache_read(). This needs more work (possibly safe, but needs
further investigation). Anyway, it's exceptional situation.
Note: probably there should be a way to disable caching of responses
if there is already one request fetching resource to cache (without waiting
at all). Two possible ways include another cache lock option ("no_cache")
or using proxy_no_cache with some supplied variable.
Note: probably there should be a way to lock updating requests as well. For
now "proxy_cache_use_stale updating" is available.
author | Maxim Dounin <mdounin@mdounin.ru> |
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date | Mon, 26 Dec 2011 11:15:23 +0000 |
parents | 3f8a2132b93d |
children | d620f497c50f |
rev | line source |
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2 /* |
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3 * Copyright (C) Igor Sysoev |
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4 */ |
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7 #include <ngx_config.h> |
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8 #include <ngx_core.h> |
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563 | 11 void |
611 | 12 ngx_spinlock(ngx_atomic_t *lock, ngx_atomic_int_t value, ngx_uint_t spin) |
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13 { |
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15 #if (NGX_HAVE_ATOMIC_OPS) |
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611 | 17 ngx_uint_t i, n; |
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19 for ( ;; ) { |
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611 | 21 if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, value)) { |
22 return; | |
23 } | |
24 | |
25 if (ngx_ncpu > 1) { | |
26 | |
27 for (n = 1; n < spin; n <<= 1) { | |
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611 | 29 for (i = 0; i < n; i++) { |
30 ngx_cpu_pause(); | |
31 } | |
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611 | 33 if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, value)) { |
34 return; | |
35 } | |
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36 } |
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37 } |
611 | 38 |
39 ngx_sched_yield(); | |
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40 } |
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41 |
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42 #else |
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44 #if (NGX_THREADS) |
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46 #error ngx_spinlock() or ngx_atomic_cmp_set() are not defined ! |
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48 #endif |
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50 #endif |
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52 } |