| Message ID | bac938d8a2d57653b9f22e55c6d222a990b6a5cf.1582301521.git.jstancek@redhat.com |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | lib: fputs() in print_result() is not signal safe | expand |
Hi! > We have tests that use tst_res() from signal handler and current > implementation leads to rare hangs if signal arrives in bad time: > main > tst_run_tcases > fork_testrun > testrun > run_tests > run > tst_res_ -> TINFO from main process > tst_vres_ > print_result > fputs > __lll_lock_wait_private > <signal handler called> > tst_res_ -> TINFO from signal handler > tst_vres_ > print_result > fputs > __lll_lock_wait_private -> HANGS > > One example is timer_settime01, where we have TPASS from main process > and TINFO as response to SIGALRM. SIGALRM happening immediately on older > kernels might be a bug, but that is beside the point of this patch. I guess that tst_res() wasn't even supposed to be signal-async-safe but looking at the code I guess that this is the only change needed to make it so. Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
Hi Jan,
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Kind regards,
Petr
----- Original Message ----- > Hi Jan, > > Reviewed-by: Petr Vorel <pvorel@suse.cz> Pushed.
diff --git a/lib/tst_test.c b/lib/tst_test.c index 9a24cffc5011..220d7fdfc548 100644 --- a/lib/tst_test.c +++ b/lib/tst_test.c @@ -181,7 +181,7 @@ static void print_result(const char *file, const int lineno, int ttype, { char buf[1024]; char *str = buf; - int ret, size = sizeof(buf), ssize, int_errno; + int ret, size = sizeof(buf), ssize, int_errno, buflen; const char *str_errno = NULL; const char *res; @@ -255,7 +255,17 @@ static void print_result(const char *file, const int lineno, int ttype, snprintf(str, size, "\n"); - fputs(buf, stderr); + /* we might be called from signal handler, so use write() */ + buflen = str - buf + 1; + str = buf; + while (buflen) { + ret = write(STDERR_FILENO, str, buflen); + if (ret <= 0) + break; + + str += ret; + buflen -= ret; + } } void tst_vres_(const char *file, const int lineno, int ttype,
We have tests that use tst_res() from signal handler and current implementation leads to rare hangs if signal arrives in bad time: main tst_run_tcases fork_testrun testrun run_tests run tst_res_ -> TINFO from main process tst_vres_ print_result fputs __lll_lock_wait_private <signal handler called> tst_res_ -> TINFO from signal handler tst_vres_ print_result fputs __lll_lock_wait_private -> HANGS One example is timer_settime01, where we have TPASS from main process and TINFO as response to SIGALRM. SIGALRM happening immediately on older kernels might be a bug, but that is beside the point of this patch. Replace fputs() with write() to avoid this hang. Signed-off-by: Jan Stancek <jstancek@redhat.com> --- lib/tst_test.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)