This patch adds a sanity check to drmWaitVBlank to prevent hangs. Since the
server interrupts syscalls pretty frequently with SIGALM, we tend to restart
syscalls when EINTR is returned. That means when a vblank timeout happens,
we probably won't catch it (it happens after 3s, and SIGALM happens every few
ms), so we can fairly easily get stuck restarting the vblank wait ioctl if
something fishy is going on (like vblank interrupts are disabled for some
reason).
So this patch removes the top level restart code, pushing it into the vblank
wait ioctl wrapper, while adding a timeout. If there are cases where more
than 1s waits are desirable, we'd probably need to check the sequence numbers
and come up with a more reasonable value, or add a new call that takes a
timeout parameter.
Any thoughts here? I chose to use clock_gettime(CLOCK_MONOTONIC..) to avoid
any issues with the TOD clock getting reset under us; I'm not sure if that's
safe everywhere and a simpler method is probably possible too...
--
Jesse Barnes, Intel Open Source Technology Center
diff --git a/libdrm/Makefile.am b/libdrm/Makefile.am
index eb63abe..71a8718 100644
--- a/libdrm/Makefile.am
+++ b/libdrm/Makefile.am
@@ -23,6 +23,7 @@ SUBDIRS = . intel
libdrm_la_LTLIBRARIES = libdrm.la
libdrm_ladir = $(libdir)
libdrm_la_LDFLAGS = -version-number 2:4:0 -no-undefined
+libdrm_la_LIBADD = -lrt
AM_CFLAGS = -I$(top_srcdir)/shared-core
libdrm_la_SOURCES = xf86drm.c xf86drmHash.c xf86drmRandom.c xf86drmSL.c \
diff --git a/libdrm/xf86drm.c b/libdrm/xf86drm.c
index 0b5d31f..00bcef4 100644
--- a/libdrm/xf86drm.c
+++ b/libdrm/xf86drm.c
@@ -42,6 +42,7 @@
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
+#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#define stat_t struct stat
@@ -184,7 +185,7 @@ drmIoctl(int fd, unsigned long request, void *arg)
do {
ret = ioctl(fd, request, arg);
- } while (ret == -1 && (errno == EINTR || errno == EAGAIN));
+ } while (ret == -1 && errno == EAGAIN);
return ret;
}
@@ -1896,13 +1897,30 @@ int drmScatterGatherFree(int fd, drm_handle_t handle)
*/
int drmWaitVBlank(int fd, drmVBlankPtr vbl)
{
+ struct timespec timeout, cur;
int ret;
+ ret = clock_gettime(CLOCK_MONOTONIC, &timeout);
+ if (ret < 0) {
+ fprintf(stderr, "clock_gettime failed: %s\n", strerror(ret));
+ goto out;
+ }
+ timeout.tv_sec++;
+
do {
ret = drmIoctl(fd, DRM_IOCTL_WAIT_VBLANK, vbl);
vbl->request.type &= ~DRM_VBLANK_RELATIVE;
+ clock_gettime(CLOCK_MONOTONIC, &cur);
+ /* Timeout after 1s */
+ if (cur.tv_sec > timeout.tv_sec + 1 ||
+ cur.tv_sec == timeout.tv_sec && cur.tv_nsec >= timeout.tv_nsec) {
+ errno = ETIME;
+ ret = -1;
+ break;
+ }
} while (ret && errno == EINTR);
+out:
return ret;
}
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