Mercurial > hg > nginx
view src/core/ngx_rwlock.c @ 9194:a6f79f044de5
QUIC: path revalidation after expansion failure.
As per RFC 9000, Section 8.2.1:
When an endpoint is unable to expand the datagram size to 1200 bytes due
to the anti-amplification limit, the path MTU will not be validated.
To ensure that the path MTU is large enough, the endpoint MUST perform a
second path validation by sending a PATH_CHALLENGE frame in a datagram of
at least 1200 bytes.
author | Roman Arutyunyan <arut@nginx.com> |
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date | Wed, 29 Nov 2023 10:58:21 +0400 |
parents | 7752d8523066 |
children |
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/* * Copyright (C) Ruslan Ermilov * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> #if (NGX_HAVE_ATOMIC_OPS) #define NGX_RWLOCK_SPIN 2048 #define NGX_RWLOCK_WLOCK ((ngx_atomic_uint_t) -1) void ngx_rwlock_wlock(ngx_atomic_t *lock) { ngx_uint_t i, n; for ( ;; ) { if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) { return; } if (ngx_ncpu > 1) { for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { for (i = 0; i < n; i++) { ngx_cpu_pause(); } if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) { return; } } } ngx_sched_yield(); } } void ngx_rwlock_rlock(ngx_atomic_t *lock) { ngx_uint_t i, n; ngx_atomic_uint_t readers; for ( ;; ) { readers = *lock; if (readers != NGX_RWLOCK_WLOCK && ngx_atomic_cmp_set(lock, readers, readers + 1)) { return; } if (ngx_ncpu > 1) { for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) { for (i = 0; i < n; i++) { ngx_cpu_pause(); } readers = *lock; if (readers != NGX_RWLOCK_WLOCK && ngx_atomic_cmp_set(lock, readers, readers + 1)) { return; } } } ngx_sched_yield(); } } void ngx_rwlock_unlock(ngx_atomic_t *lock) { if (*lock == NGX_RWLOCK_WLOCK) { (void) ngx_atomic_cmp_set(lock, NGX_RWLOCK_WLOCK, 0); } else { (void) ngx_atomic_fetch_add(lock, -1); } } void ngx_rwlock_downgrade(ngx_atomic_t *lock) { if (*lock == NGX_RWLOCK_WLOCK) { *lock = 1; } } #else #if (NGX_HTTP_UPSTREAM_ZONE || NGX_STREAM_UPSTREAM_ZONE) #error ngx_atomic_cmp_set() is not defined! #endif #endif