summaryrefslogtreecommitdiffstats
path: root/COPYING
diff options
context:
space:
mode:
authorAndrea Arcangeli <aarcange@redhat.com>2015-09-05 00:47:18 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2015-09-05 01:54:41 +0200
commitdfa37dc3fc1f6f81a6900d0e561c02362f4817f6 (patch)
treeec3267d5e11f9c8ca774e52c827e757d3a228d52 /COPYING
parentuserfaultfd: require UFFDIO_API before other ioctls (diff)
downloadlinux-dfa37dc3fc1f6f81a6900d0e561c02362f4817f6.tar.xz
linux-dfa37dc3fc1f6f81a6900d0e561c02362f4817f6.zip
userfaultfd: allow signals to interrupt a userfault
This is only simple to achieve if the userfault is going to return to userland (not to the kernel) because we can avoid returning VM_FAULT_RETRY despite we temporarily released the mmap_sem. The fault would just be retried by userland then. This is safe at least on x86 and powerpc (the two archs with the syscall implemented so far). Hint to verify for which archs this is safe: after handle_mm_fault returns, no access to data structures protected by the mmap_sem must be done by the fault code in arch/*/mm/fault.c until up_read(&mm->mmap_sem) is called. This has two main benefits: signals can run with lower latency in production (signals aren't blocked by userfaults and userfaults are immediately repeated after signal processing) and gdb can then trivially debug the threads blocked in this kind of userfaults coming directly from userland. On a side note: while gdb has a need to get signal processed, coredumps always worked perfectly with userfaults, no matter if the userfault is triggered by GUP a kernel copy_user or directly from userland. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'COPYING')
0 files changed, 0 insertions, 0 deletions