From: Dave Hansen <[email protected]> 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: Ram Pai <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Michael Ellermen <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Shuah Khan <[email protected]> --- b/tools/testing/selftests/x86/pkey-helpers.h | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) diff -puN tools/testing/selftests/x86/pkey-helpers.h~pkeys-selftests-avoid-print-in-signal-deadlocks tools/testing/selftests/x86/pkey-helpers.h --- a/tools/testing/selftests/x86/pkey-helpers.h~pkeys-selftests-avoid-print-in-signal-deadlocks 2018-05-09 09:20:19.738698404 -0700 +++ b/tools/testing/selftests/x86/pkey-helpers.h 2018-05-09 09:20:19.742698404 -0700 @@ -26,30 +26,26 @@ static inline void sigsafe_printf(const { 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) _
