Merge tag 'for-linus-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml

Pull UML updates from Richard Weinberger:

 - A new timer mode, time travel, for testing with UML

 - Many bugixes/improvements for the serial line driver

 - Various bugfixes

* tag 'for-linus-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml:
  um: fix build without CONFIG_UML_TIME_TRAVEL_SUPPORT
  um: Fix kcov crash during startup
  um: configs: Remove useless UEVENT_HELPER_PATH
  um: Support time travel mode
  um: Pass nsecs to os timer functions
  um: Remove drivers/ssl.h
  um: Don't garbage collect in deactivate_all_fds()
  um: Silence lockdep complaint about mmap_sem
  um: Remove locking in deactivate_all_fds()
  um: Timer code cleanup
  um: fix os_timer_one_shot()
  um: Fix IRQ controller regression on console read

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index b783ac87d98a..44bb10785075 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -10,12 +10,23 @@
 #include <sysdep/ptrace.h>
 #include <sysdep/ptrace_user.h>
 #include <sysdep/syscalls.h>
+#include <shared/timer-internal.h>
 
 void handle_syscall(struct uml_pt_regs *r)
 {
         struct pt_regs *regs = container_of(r, struct pt_regs, regs);
         int syscall;
 
+        /*
+         * If we have infinite CPU resources, then make every syscall also a
+         * preemption point, since we don't have any other preemption in this
+         * case, and kernel threads would basically never run until userspace
+         * went to sleep, even if said userspace interacts with the kernel in
+         * various ways.
+         */
+        if (time_travel_mode == TT_MODE_INFCPU)
+                schedule();
+
         /* Initialize the syscall number and default return value. */
         UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
         PT_REGS_SET_SYSCALL_RETURN(regs, -ENOSYS);