x86/pkeys/selftests: Avoid printf-in-signal deadlocks

printf() and friends are unusable in signal handlers.  They deadlock.
The pkey selftest does not do any normal printing in signal handlers,
only extra debugging.  So, just print the format string so we get
*some* output when debugging.

Signed-off-by: Dave Hansen <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Michael Ellermen <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ram Pai <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 8 insertions, 12 deletions

diff --git a/tools/testing/selftests/x86/pkey-helpers.h b/tools/testing/selftests/x86/pkey-helpers.h
index b3cb7670e026..254e5436bdd9 100644
--- a/tools/testing/selftests/x86/pkey-helpers.h
+++ b/tools/testing/selftests/x86/pkey-helpers.h
@@ -26,30 +26,26 @@ static inline void sigsafe_printf(const char *format, ...)
 {
 	va_list ap;
 
-	va_start(ap, format);
 	if (!dprint_in_signal) {
+		va_start(ap, format);
 		vprintf(format, ap);
+		va_end(ap);
 	} else {
 		int ret;
-		int len = vsnprintf(dprint_in_signal_buffer,
-				    DPRINT_IN_SIGNAL_BUF_SIZE,
-				    format, ap);
 		/*
-		 * len is amount that would have been printed,
-		 * but actual write is truncated at BUF_SIZE.
+		 * No printf() functions are signal-safe.
+		 * They deadlock easily. Write the format
+		 * string to get some output, even if
+		 * incomplete.
 		 */
-		if (len > DPRINT_IN_SIGNAL_BUF_SIZE)
-			len = DPRINT_IN_SIGNAL_BUF_SIZE;
-		ret = write(1, dprint_in_signal_buffer, len);
+		ret = write(1, format, strlen(format));
 		if (ret < 0)
-			abort();
+			exit(1);
 	}
-	va_end(ap);
 }
 #define dprintf_level(level, args...) do {	\
 	if (level <= DEBUG_LEVEL)		\
 		sigsafe_printf(args);		\
-	fflush(NULL);				\
 } while (0)
 #define dprintf0(args...) dprintf_level(0, args)
 #define dprintf1(args...) dprintf_level(1, args)