powerpc/spufs: Fix spinning in spufs_ps_fault on signal

Currently, we can end up in an infinite loop if we get a signal
while the kernel has faulted in spufs_ps_fault. Eg:

 alarm(1);

 write(fd, some_spu_psmap_register_address, 4);

- the write's copy_from_user will fault on the ps mapping, and
signal_pending will be non-zero. Because returning from the fault
handler will never clear TIF_SIGPENDING, so we'll just keep faulting,
resulting in an unkillable process using 100% of CPU.

This change returns VM_FAULT_SIGBUS if there's a fatal signal pending,
letting us escape the loop.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index b73c369cc6f167a4fa52c9162cfed557c9c1bba0..1b26071a86ca8f17e1f2c04f22ffb9d60d13e2b8 100644 (file)
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -390,6 +390,9 @@ static int spufs_ps_fault(struct vm_area_struct *vma,
        if (offset >= ps_size)
                return VM_FAULT_SIGBUS;
 
+       if (fatal_signal_pending(current))
+               return VM_FAULT_SIGBUS;
+
        /*
         * Because we release the mmap_sem, the context may be destroyed while
         * we're in spu_wait. Grab an extra reference so it isn't destroyed