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commit a8cac598647384069aa1a834cf9670318759b772 Author: Xiang Xiao <[email protected]> AuthorDate: Fri Apr 1 12:26:30 2022 +0800 libc/netdb: Support the recursive lock Signed-off-by: Xiang Xiao <[email protected]> --- libs/libc/netdb/lib_dnsinit.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) diff --git a/libs/libc/netdb/lib_dnsinit.c b/libs/libc/netdb/lib_dnsinit.c index 5b07f5aa59..ae45b82142 100644 --- a/libs/libc/netdb/lib_dnsinit.c +++ b/libs/libc/netdb/lib_dnsinit.c @@ -30,6 +30,7 @@ #include <arpa/inet.h> +#include <nuttx/sched.h> #include <nuttx/semaphore.h> #include "netdb/lib_dns.h" @@ -40,7 +41,9 @@ /* Protects DNS cache, nameserver list and notify list. */ -static sem_t g_dns_sem = SEM_INITIALIZER(1); +static sem_t g_dns_sem = SEM_INITIALIZER(1); +static pid_t g_dns_holder = INVALID_PROCESS_ID; +static int g_dns_count; /**************************************************************************** * Public Data @@ -143,9 +146,20 @@ bool dns_initialize(void) void dns_semtake(void) { + pid_t me = getpid(); int errcode = 0; int ret; + /* Does this thread already hold the semaphore? */ + + if (g_dns_holder == me) + { + /* Yes.. just increment the reference count */ + + g_dns_count++; + return; + } + do { ret = _SEM_WAIT(&g_dns_sem); @@ -156,6 +170,9 @@ void dns_semtake(void) } } while (ret < 0 && errcode == EINTR); + + g_dns_holder = me; + g_dns_count = 1; } /**************************************************************************** @@ -168,5 +185,11 @@ void dns_semtake(void) void dns_semgive(void) { - DEBUGVERIFY(_SEM_POST(&g_dns_sem)); + DEBUGASSERT(g_dns_holder == getpid() && g_dns_count > 0); + + if (--g_dns_count == 0) + { + g_dns_holder = INVALID_PROCESS_ID; + DEBUGVERIFY(_SEM_POST(&g_dns_sem)); + } }
