kernel/arch/um/os-Linux/sigio.c, branch linux-rolling-stable

um: Fix tgkill compile error on old host OSes

2025-06-19T13:40:39Z

[ Upstream commit fd054188999ff19746cc09f4e0f196a113964db9 ] tgkill is a quite old syscall since kernel 2.5.75, but unfortunately glibc doesn't support it before 2.30. Thus some systems fail to compile the latest UserMode Linux. Here is the compile error I encountered when I tried to compile UML in my system shipped with glibc-2.28. CALL scripts/checksyscalls.sh CC arch/um/os-Linux/sigio.o In file included from arch/um/os-Linux/sigio.c:17: arch/um/os-Linux/sigio.c: In function ‘write_sigio_thread’: arch/um/os-Linux/sigio.c:49:19: error: implicit declaration of function ‘tgkill’; did you mean ‘kill’? [-Werror=implicit-function-declaration] CATCH_EINTR(r = tgkill(pid, pid, SIGIO)); ^~~~~~ ./arch/um/include/shared/os.h:21:48: note: in definition of macro ‘CATCH_EINTR’ #define CATCH_EINTR(expr) while ((errno = 0, ((expr) < 0)) && (errno == EINTR)) ^~~~ cc1: some warnings being treated as errors Fix it by Replacing glibc call with raw syscall. Fixes: 33c9da5dfb18 ("um: Rewrite the sigio workaround based on epoll and tgkill") Signed-off-by: Yongting Lin Link: https://patch.msgid.link/20250527151222.40371-1-linyongting@gmail.com Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

um: Rewrite the sigio workaround based on epoll and tgkill

2025-03-20T08:28:44Z

The existing sigio workaround implementation removes FDs from the poll when events are triggered, requiring users to re-add them via add_sigio_fd() after processing. This introduces a potential race condition between FD removal in write_sigio_thread() and next_poll update in __add_sigio_fd(), and is inefficient due to frequent FD removal and re-addition. Rewrite the implementation based on epoll and tgkill for improved efficiency and reliability. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20250315161910.4082396-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg

um: Switch to the pthread-based helper in sigio workaround

2025-03-20T08:26:38Z

The write_sigio thread and UML kernel thread share the same errno, which can lead to conflicts when both call syscalls concurrently. Switch to the pthread-based helper to address this issue. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20250319135523.97050-4-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg

um: Set parent-death signal for write_sigio thread/process

2024-10-25T09:34:55Z

The write_sigio thread is not really a traditional thread. Set the parent-death signal for it to ensure that it will be killed if the UML kernel dies unexpectedly without proper cleanup. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20241024142828.2612828-4-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg

Revert "um: Use swap() to make code cleaner"

2023-07-27T20:07:03Z

This reverts commit 9b0da3f22307af693be80f5d3a89dc4c7f360a85. The sigio.c is clearly user space code which is handled by arch/um/scripts/Makefile.rules (see USER_OBJS rule). The above mentioned commit simply broke this agreement, we may not use Linux kernel internal headers in them without thorough thinking. Hence, revert the wrong commit. Link: https://lkml.kernel.org/r/20230724143131.30090-1-andriy.shevchenko@linux.intel.com Signed-off-by: Andy Shevchenko Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202307212304.cH79zJp1-lkp@intel.com/ Cc: Anton Ivanov Cc: Herve Codina Cc: Jason A. Donenfeld Cc: Johannes Berg Cc: Rasmus Villemoes Cc: Richard Weinberger Cc: Yang Guang Cc: Signed-off-by: Andrew Morton

um: Use swap() to make code cleaner

2021-12-21T20:41:04Z

Use the macro 'swap()' defined in 'include/linux/minmax.h' to avoid opencoding it. Reported-by: Zeal Robot Signed-off-by: Yang Guang Signed-off-by: Richard Weinberger

um: rename set_signals() to um_set_signals()

2021-12-21T20:13:44Z

Rename set_signals() as there's at least one driver that uses the same name and can now be built on UM due to PCI support, and thus we can get symbol conflicts. Also rename set_signals_trace() to be consistent. Reported-by: kernel test robot Fixes: 68f5d3f3b654 ("um: add PCI over virtio emulation driver") Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: irq/sigio: Support suspend/resume handling of workaround IRQs

2020-12-13T21:42:01Z

If the sigio workaround needed to be applied to a file descriptor, set_irq_wake() wouldn't work for it since it would get polled by the thread instead of causing SIGIO, and thus could never really cause a wakeup, since the thread notification FD wasn't marked as being able to wake up the system. Fix this by marking the thread's notification FD explicitly as a wake source FD, i.e. not suppressing SIGIO for it in suspend. In order to not cause spurious wakeups, we then need to remove all FDs that shouldn't wake up the system from the polling thread. In order to do this, add unlocked versions of ignore_sigio_fd() and add_sigio_fd() (nothing else is happening in suspend, so this is fine), and also modify ignore_sigio_fd() to return -ENOENT if the FD wasn't originally in there. This doesn't matter because nothing else currently checks the return value, but the irq code needs to know which ones to restore the workaround for. All told, this lets us use a timerfd for the RTC clock in the next patch, which doesn't send SIGIO. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: Remove IRQ_NONE type

2020-12-13T21:22:29Z

We don't actually use this in um_request_irq(), so it can never be assigned. It's also not clear what that would be useful for, so just remove it. This results in quite a number of cleanups, all the way to removing the "SIGIO on close" startup check, since the data it assigns (pty_close_sigio) is not used anymore. While at it, also make this an enum so we get a minimum of type checking, and remove the IRQ_NONE hack in virtio since we now no longer have the name twice. Acked-By: Anton Ivanov Signed-off-by: Johannes Berg Acked-By: Anton Ivanov Signed-off-by: Richard Weinberger

um: sigio: Return error from add_sigio_fd()

2020-12-13T21:22:01Z

If we run out of space, return an error instead of 0. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger