<div dir="ltr"><div>I'd rather have something more robust than an env var, like catching SIGSYS. </div><div> </div><div>Marek </div></div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Feb 27, 2019 at 6:13 PM <<a href="mailto:marcandre.lureau@redhat.com">marcandre.lureau@redhat.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">From: Marc-André Lureau <<a href="mailto:marcandre.lureau@redhat.com" target="_blank">marcandre.lureau@redhat.com</a>> Since commit d877451b48a59ab0f9a4210fc736f51da5851c9a ("util/u_queue: add UTIL_QUEUE_INIT_SET_FULL_THREAD_AFFINITY"), mesa calls sched_setaffinity syscall. Unfortunately, qemu crashes with SIGSYS when sandboxing is enabled (by default with libvirt), as this syscall is filtered. There doesn't seem to be a way to check for the seccomp rule other than doing a call, which may result in various behaviour depending on seccomp actions. There is a PTRACE_SECCOMP_GET_FILTER, but it is low-level and a priviledged operation (but there might be a way to use it?). A safe way would be to try the call in a subprocess, unfortunately, qemu also prohibits fork(). Also this could be subject to TOCTOU. There seems to be few solutions, but the issue can be considered a regression for various libvirt/Boxes users. Introduce MESA_NO_THREAD_AFFINITY environment variable to prevent the offending call. Wrap pthread_setaffinity_np() in a utility function u_pthread_setaffinity_np(), returning a EACCESS error if the variable is set. Note: one call is left with a FIXME, as I didn't investigate how to build and test it, help welcome! See also: <a href="https://bugs.freedesktop.org/show_bug.cgi?id=109695" rel="noreferrer" target="_blank">https://bugs.freedesktop.org/show_bug.cgi?id=109695</a> Signed-off-by: Marc-André Lureau <<a href="mailto:marcandre.lureau@redhat.com" target="_blank">marcandre.lureau@redhat.com</a>> --- .../drivers/swr/rasterizer/core/threads.cpp | 1 + src/util/u_queue.c | 2 +- src/util/u_thread.h | 15 ++++++++++++++- 3 files changed, 16 insertions(+), 2 deletions(-) diff --git a/src/gallium/drivers/swr/rasterizer/core/threads.cpp b/src/gallium/drivers/swr/rasterizer/core/threads.cpp index e30c1170568..d10c79512a1 100644 --- a/src/gallium/drivers/swr/rasterizer/core/threads.cpp +++ b/src/gallium/drivers/swr/rasterizer/core/threads.cpp @@ -364,6 +364,7 @@ void bindThread(SWR_CONTEXT* pContext, CPU_ZERO(&cpuset); CPU_SET(threadId, &cpuset); + /* FIXME: use u_pthread_setaffinity_np() if possible */ int err = pthread_setaffinity_np(thread, sizeof(cpu_set_t), &cpuset); if (err != 0) { diff --git a/src/util/u_queue.c b/src/util/u_queue.c index 3812c824b6d..dea8d2bb4ae 100644 --- a/src/util/u_queue.c +++ b/src/util/u_queue.c @@ -249,7 +249,7 @@ util_queue_thread_func(void *input) for (unsigned i = 0; i < CPU_SETSIZE; i++) CPU_SET(i, &cpuset); - pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset); + u_pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset); } #endif diff --git a/src/util/u_thread.h b/src/util/u_thread.h index a46c18d3db2..a4e6dbae5d7 100644 --- a/src/util/u_thread.h +++ b/src/util/u_thread.h @@ -70,6 +70,19 @@ static inline void u_thread_setname( const char *name ) (void)name; } +#if defined(HAVE_PTHREAD_SETAFFINITY) +static inline int u_pthread_setaffinity_np(pthread_t thread, size_t cpusetsize, + const cpu_set_t *cpuset) +{ + if (getenv("MESA_NO_THREAD_AFFINITY")) { + errno = EACCES; + return -1; + } + + return pthread_setaffinity_np(thread, cpusetsize, cpuset); +} +#endif + /** * An AMD Zen CPU consists of multiple modules where each module has its own L3 * cache. Inter-thread communication such as locks and atomics between modules @@ -89,7 +102,7 @@ util_pin_thread_to_L3(thrd_t thread, unsigned L3_index, unsigned cores_per_L3) CPU_ZERO(&cpuset); for (unsigned i = 0; i < cores_per_L3; i++) CPU_SET(L3_index * cores_per_L3 + i, &cpuset); - pthread_setaffinity_np(thread, sizeof(cpuset), &cpuset); + u_pthread_setaffinity_np(thread, sizeof(cpuset), &cpuset); #endif } -- 2.21.0 _______________________________________________ mesa-dev mailing list <a href="mailto:mesa-dev@lists.freedesktop.org" target="_blank">mesa-dev@lists.freedesktop.org</a> <a href="https://lists.freedesktop.org/mailman/listinfo/mesa-dev" rel="noreferrer" target="_blank">https://lists.freedesktop.org/mailman/listinfo/mesa-dev</a></blockquote></div>