Produce the stack trace in an async safe way.

[redis.git] / src / debug.c

diff --git a/src/debug.c b/src/debug.c
index 30fb00915982dbf37e51bc97df30444db16aa07f..42a73883d9d6f0f7ef3eba8511ab7f750de7428b 100644 (file)
--- a/src/debug.c
+++ b/src/debug.c
@@ -7,6 +7,7 @@
 #ifdef HAVE_BACKTRACE
 #include <execinfo.h>
 #include <ucontext.h>
+#include <fcntl.h>
 #endif /* HAVE_BACKTRACE */
 
 /* ================================= Debugging ============================== */
@@ -105,7 +106,6 @@ void computeDatasetDigest(unsigned char *final) {
 
             mixDigest(digest,key,sdslen(key));
 
-            /* Make sure the key is loaded if VM is active */
             o = dictGetVal(de);
 
             aux = htonl(o->type);
@@ -399,30 +399,31 @@ void bugReportStart(void) {
 
 #ifdef HAVE_BACKTRACE
 static void *getMcontextEip(ucontext_t *uc) {
-#if defined(__FreeBSD__)
-    return (void*) uc->uc_mcontext.mc_eip;
-#elif defined(__dietlibc__)
-    return (void*) uc->uc_mcontext.eip;
-#elif defined(__APPLE__) && !defined(MAC_OS_X_VERSION_10_6)
-  #if __x86_64__
+#if defined(__APPLE__) && !defined(MAC_OS_X_VERSION_10_6)
+    /* OSX < 10.6 */
+    #if defined(__x86_64__)
     return (void*) uc->uc_mcontext->__ss.__rip;
-  #elif __i386__
+    #elif defined(__i386__)
     return (void*) uc->uc_mcontext->__ss.__eip;
-  #else
+    #else
     return (void*) uc->uc_mcontext->__ss.__srr0;
-  #endif
+    #endif
 #elif defined(__APPLE__) && defined(MAC_OS_X_VERSION_10_6)
-  #if defined(_STRUCT_X86_THREAD_STATE64) && !defined(__i386__)
+    /* OSX >= 10.6 */
+    #if defined(_STRUCT_X86_THREAD_STATE64) && !defined(__i386__)
     return (void*) uc->uc_mcontext->__ss.__rip;
-  #else
+    #else
     return (void*) uc->uc_mcontext->__ss.__eip;
-  #endif
-#elif defined(__i386__)
+    #endif
+#elif defined(__linux__)
+    /* Linux */
+    #if defined(__i386__)
     return (void*) uc->uc_mcontext.gregs[14]; /* Linux 32 */
-#elif defined(__X86_64__) || defined(__x86_64__)
+    #elif defined(__X86_64__) || defined(__x86_64__)
     return (void*) uc->uc_mcontext.gregs[16]; /* Linux 64 */
-#elif defined(__ia64__) /* Linux IA64 */
+    #elif defined(__ia64__) /* Linux IA64 */
     return (void*) uc->uc_mcontext.sc_ip;
+    #endif
 #else
     return NULL;
 #endif
@@ -440,8 +441,11 @@ void logStackContent(void **sp) {
 
 void logRegisters(ucontext_t *uc) {
     redisLog(REDIS_WARNING, "--- REGISTERS");
+
+/* OSX */
 #if defined(__APPLE__) && defined(MAC_OS_X_VERSION_10_6)
-  #if defined(_STRUCT_X86_THREAD_STATE64) && !defined(__i386__)
+  /* OSX AMD64 */
+    #if defined(_STRUCT_X86_THREAD_STATE64) && !defined(__i386__)
     redisLog(REDIS_WARNING,
     "\n"
     "RAX:%016lx RBX:%016lx\nRCX:%016lx RDX:%016lx\n"
@@ -472,7 +476,8 @@ void logRegisters(ucontext_t *uc) {
         uc->uc_mcontext->__ss.__gs
     );
     logStackContent((void**)uc->uc_mcontext->__ss.__rsp);
-  #else
+    #else
+    /* OSX x86 */
     redisLog(REDIS_WARNING,
     "\n"
     "EAX:%08lx EBX:%08lx ECX:%08lx EDX:%08lx\n"
@@ -497,8 +502,11 @@ void logRegisters(ucontext_t *uc) {
         uc->uc_mcontext->__ss.__gs
     );
     logStackContent((void**)uc->uc_mcontext->__ss.__esp);
-  #endif
-#elif defined(__i386__)
+    #endif
+/* Linux */
+#elif defined(__linux__)
+    /* Linux x86 */
+    #if defined(__i386__)
     redisLog(REDIS_WARNING,
     "\n"
     "EAX:%08lx EBX:%08lx ECX:%08lx EDX:%08lx\n"
@@ -523,7 +531,8 @@ void logRegisters(ucontext_t *uc) {
         uc->uc_mcontext.gregs[0]
     );
     logStackContent((void**)uc->uc_mcontext.gregs[7]);
-#elif defined(__X86_64__) || defined(__x86_64__)
+    #elif defined(__X86_64__) || defined(__x86_64__)
+    /* Linux AMD64 */
     redisLog(REDIS_WARNING,
     "\n"
     "RAX:%016lx RBX:%016lx\nRCX:%016lx RDX:%016lx\n"
@@ -552,29 +561,37 @@ void logRegisters(ucontext_t *uc) {
         uc->uc_mcontext.gregs[18]
     );
     logStackContent((void**)uc->uc_mcontext.gregs[15]);
+    #endif
 #else
     redisLog(REDIS_WARNING,
         "  Dumping of registers not supported for this OS/arch");
 #endif
 }
 
-/* Logs the stack trace using the backtrace() call. */
+/* Logs the stack trace using the backtrace() call. This function is designed
+ * to be called from signal handlers safely. */
 void logStackTrace(ucontext_t *uc) {
     void *trace[100];
-    int i, trace_size = 0;
-    char **messages = NULL;
+    int trace_size = 0, fd;
+
+    /* Open the log file in append mode. */
+    fd = server.logfile ?
+        open(server.logfile, O_APPEND|O_CREAT|O_WRONLY, 0644) :
+        STDOUT_FILENO;
+    if (fd == -1) return;
 
     /* Generate the stack trace */
     trace_size = backtrace(trace, 100);
 
     /* overwrite sigaction with caller's address */
-    if (getMcontextEip(uc) != NULL) {
+    if (getMcontextEip(uc) != NULL)
         trace[1] = getMcontextEip(uc);
-    }
-    messages = backtrace_symbols(trace, trace_size);
-    redisLog(REDIS_WARNING, "--- STACK TRACE");
-    for (i=1; i<trace_size; ++i)
-        redisLog(REDIS_WARNING,"%s", messages[i]);
+
+    /* Write symbols to log file */
+    backtrace_symbols_fd(trace, trace_size, fd);
+
+    /* Cleanup */
+    if (server.logfile) close(fd);
 }
 
 /* Log information about the "current" client, that is, the client that is
@@ -629,6 +646,7 @@ void sigsegvHandler(int sig, siginfo_t *info, void *secret) {
                         server.assert_file, server.assert_line);
 
     /* Log the stack trace */
+    redisLog(REDIS_WARNING, "--- STACK TRACE");
     logStackTrace(uc);
 
     /* Log INFO and CLIENT LIST */
@@ -672,16 +690,19 @@ void sigsegvHandler(int sig, siginfo_t *info, void *secret) {
 #include <sys/time.h>
 
 void watchdogSignalHandler(int sig, siginfo_t *info, void *secret) {
+#ifdef HAVE_BACKTRACE
     ucontext_t *uc = (ucontext_t*) secret;
+#endif
     REDIS_NOTUSED(info);
     REDIS_NOTUSED(sig);
 
-    /* Log INFO and CLIENT LIST */
-    redisLog(REDIS_WARNING, "--- WATCHDOG TIMER EXPIRED ---"); 
+    redisLogFromHandler(REDIS_WARNING,"\n--- WATCHDOG TIMER EXPIRED ---");
 #ifdef HAVE_BACKTRACE
     logStackTrace(uc);
-    redisLog(REDIS_WARNING, "------");
+#else
+    redisLogFromHandler(REDIS_WARNING,"Sorry: no support for backtrace().");
 #endif
+    redisLogFromHandler(REDIS_WARNING,"--------\n");
 }
 
 /* Schedule a SIGALRM delivery after the specified period in milliseconds.