Calling OsReleaseSignal() inside the signal handler releases SIGIO, causing the signal handler to be called again from within the handler.
Practical use-case: when synaptics calls TimerSet in the signal handler, this causes the signals to be released, eventually hanging the server. Regression introduced in 08962951de. Signed-off-by: Peter Hutterer <[email protected]> --- os/utils.c | 9 +++++---- test/os.c | 36 ++++++++++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+), 4 deletions(-) diff --git a/os/utils.c b/os/utils.c index cb37162..afd50b3 100644 --- a/os/utils.c +++ b/os/utils.c @@ -1186,6 +1186,7 @@ OsBlockSignals(void) #ifdef SIG_BLOCK static sig_atomic_t sigio_blocked; +static sigset_t PreviousSigIOMask; #endif /** @@ -1198,13 +1199,13 @@ OsBlockSIGIO(void) #ifdef SIGIO #ifdef SIG_BLOCK if (sigio_blocked++ == 0) { - sigset_t set, old; + sigset_t set; int ret; sigemptyset(&set); sigaddset(&set, SIGIO); - sigprocmask(SIG_BLOCK, &set, &old); - ret = sigismember(&old, SIGIO); + sigprocmask(SIG_BLOCK, &set, &PreviousSigIOMask); + ret = sigismember(&PreviousSigIOMask, SIGIO); return ret; } else return 1; @@ -1222,7 +1223,7 @@ OsReleaseSIGIO(void) sigemptyset(&set); sigaddset(&set, SIGIO); - sigprocmask(SIG_UNBLOCK, &set, NULL); + sigprocmask(SIG_SETMASK, &PreviousSigIOMask, 0); } else if (sigio_blocked < 0) { BUG_WARN(sigio_blocked < 0); sigio_blocked = 0; diff --git a/test/os.c b/test/os.c index 1460a34..8f1107d 100644 --- a/test/os.c +++ b/test/os.c @@ -28,6 +28,21 @@ #include <signal.h> #include "os.h" +static int last_signal = 0; +static int expect_signal = 0; + +static void sighandler(int signal) +{ + assert(expect_signal); + expect_signal = 0; + if (!last_signal) + raise(signal); + OsBlockSignals(); + OsReleaseSignals(); + last_signal = 1; + expect_signal = 1; +} + static int sig_is_blocked(int sig) { @@ -118,7 +133,27 @@ static void block_sigio_test(void) assert(sig_is_blocked(SIGIO)); OsReleaseSignals(); assert(!sig_is_blocked(SIGIO)); +#endif +} +static void block_sigio_test_nested(void) +{ +#ifdef SIG_BLOCK + /* Check for bug releasing SIGIO during SIGIO signal handling. + test case: + raise signal + → in signal handler: + raise signal + OsBlockSignals() + OsReleaseSignals() + tail guard + tail guard must be hit. + */ + sighandler_t old_handler; + old_handler = signal(SIGIO, sighandler); + expect_signal = 1; + assert(raise(SIGIO) == 0); + assert(signal(SIGIO, old_handler) == sighandler); #endif } @@ -126,5 +161,6 @@ int main(int argc, char **argv) { block_sigio_test(); + block_sigio_test_nested(); return 0; } -- 1.7.10.4 _______________________________________________ [email protected]: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel
