From a61789a1d62fd71c751189faf5371740dd375f33 Mon Sep 17 00:00:00 2001 From: Christopher Faulet Date: Fri, 19 Mar 2021 15:16:28 +0100 Subject: [PATCH] MEDIUM: lua: Use a per-thread counter to track some non-reentrant parts of lua Some parts of the Lua are non-reentrant. We must be sure to carefully track these parts to not dump the lua stack when it is interrupted inside such parts. For now, we only identified the custom lua allocator. If the thread is interrupted during the memory allocation, we must not try to print the lua stack wich also allocate memory. Indeed, realloc() is not async-signal-safe. In this patch we introduce a thread-local counter. It is incremented before entering in a non-reentrant part and decremented when exiting. It is only performed in hlua_alloc() for now. --- include/haproxy/hlua.h | 1 + src/hlua.c | 13 +++++++++++-- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/include/haproxy/hlua.h b/include/haproxy/hlua.h index 6aca17f398..36629e6370 100644 --- a/include/haproxy/hlua.h +++ b/include/haproxy/hlua.h @@ -50,6 +50,7 @@ void hlua_applet_tcp_fct(struct appctx *ctx); void hlua_applet_http_fct(struct appctx *ctx); struct task *hlua_process_task(struct task *task, void *context, unsigned int state); +extern THREAD_LOCAL unsigned int hlua_not_dumpable; #else /* USE_LUA */ /************************ For use when Lua is disabled ********************/ diff --git a/src/hlua.c b/src/hlua.c index 42d5be2a5a..962195a607 100644 --- a/src/hlua.c +++ b/src/hlua.c @@ -274,6 +274,9 @@ struct hlua_mem_allocator { static struct hlua_mem_allocator hlua_global_allocator THREAD_ALIGNED(64); + /* > 0 if lua is in a non-rentrant part, thus with a non-dumpable stack */ +THREAD_LOCAL unsigned int hlua_not_dumpable = 0; + /* These functions converts types between HAProxy internal args or * sample and LUA types. Another function permits to check if the * LUA stack contains arguments according with an required ARG_T @@ -8634,8 +8637,12 @@ static void *hlua_alloc(void *ud, void *ptr, size_t osize, size_t nsize) /* a limit of ~0 means unlimited and boot complete, so there's no need * for accounting anymore. */ - if (likely(~zone->limit == 0)) - return realloc(ptr, nsize); + if (likely(~zone->limit == 0)) { + hlua_not_dumpable++; + ptr = realloc(ptr, nsize); + hlua_not_dumpable--; + return ptr; + } if (!ptr) osize = 0; @@ -8649,7 +8656,9 @@ static void *hlua_alloc(void *ud, void *ptr, size_t osize, size_t nsize) return NULL; } while (!_HA_ATOMIC_CAS(&zone->allocated, &old, new)); + hlua_not_dumpable++; ptr = realloc(ptr, nsize); + hlua_not_dumpable--; if (unlikely(!ptr && nsize)) // failed _HA_ATOMIC_SUB(&zone->allocated, nsize - osize);