From: Pierre-Marc Fournier Date: Mon, 28 Sep 2009 23:49:53 +0000 (-0400) Subject: usterr: make error reporting functions signal safe X-Git-Tag: v1.9.1~887 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=ff1fedb9f2e8;p=lttng-ust.git usterr: make error reporting functions signal safe Previously, they could cause corruption / lockings --- diff --git a/share/usterr.h b/share/usterr.h index a1a9dac2..1819f973 100644 --- a/share/usterr.h +++ b/share/usterr.h @@ -5,6 +5,9 @@ #include #include #include +#include + +#include "share.h" #ifndef UST_COMPONENT //#error UST_COMPONENT is undefined @@ -15,9 +18,34 @@ #define XSTR(d) STR(d) #define STR(s) #s +/* We sometimes print in the tracing path, and tracing can occur in + * signal handlers, so we must use a print method which is signal safe. + */ + +#define sigsafe_print_err(fmt, args...) \ +{ \ + /* Can't use dynamic allocation. Limit ourselves to 250 chars. */ \ + char ____buf[250]; \ + int ____saved_errno; \ +\ + /* Save the errno. */ \ + ____saved_errno = errno; \ +\ + snprintf(____buf, sizeof(____buf), fmt, ## args); \ +\ + /* Add end of string in case of buffer overflow. */ \ + ____buf[sizeof(____buf)-1] = 0; \ +\ + patient_write(STDERR_FILENO, ____buf, strlen(____buf)); \ + /* Can't print errors because we are in the error printing code path. */ \ +\ + /* Restore errno, in order to be async-signal safe. */ \ + errno = ____saved_errno; \ +} + #define UST_STR_COMPONENT XSTR(UST_COMPONENT) -#define ERRMSG(fmt, args...) do { fprintf(stderr, UST_STR_COMPONENT "[%ld/%ld]: " fmt " (" __FILE__ ":" XSTR(__LINE__) ")\n", (long) getpid(), (long) syscall(SYS_gettid), ## args); fflush(stderr); } while(0) +#define ERRMSG(fmt, args...) do { sigsafe_print_err(UST_STR_COMPONENT "[%ld/%ld]: " fmt " (" __FILE__ ":" XSTR(__LINE__) ")\n", (long) getpid(), (long) syscall(SYS_gettid), ## args); fflush(stderr); } while(0) #define DEBUG #ifdef DEBUG