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[POWERPC] spufs: fix context destruction during psmap fault

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We have a small window where a spu context may be destroyed while
we're servicing a page fault (from another thread) to the context's
problem state mapping.

After we up_read() the mmap_sem, it's possible that the context is
destroyed by its owning thread, and so the later references to ctx
are invalid. This can maifest as a deadlock on the (now free()-ed)
context state mutex.

This change adds a reference to the context before we release the
mmap_sem, so that the context cannot be destroyed.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
This commit is contained in:
Jeremy Kerr 2008-02-26 13:31:42 +11:00
parent 61b36fc1f7
commit d58831375d
1 changed files with 11 additions and 1 deletions
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12
arch/powerpc/platforms/cell/spufs/file.c
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@ -366,6 +366,13 @@ static unsigned long spufs_ps_nopfn(struct vm_area_struct *vma,
if (offset >= ps_size)
return NOPFN_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
* in the meantime.
*/
get_spu_context(ctx);
/*
* We have to wait for context to be loaded before we have
* pages to hand out to the user, but we don't want to wait
@ -375,7 +382,7 @@ static unsigned long spufs_ps_nopfn(struct vm_area_struct *vma,
* hanged.
*/
if (spu_acquire(ctx))
return NOPFN_REFAULT;
goto refault;
if (ctx->state == SPU_STATE_SAVED) {
up_read(&current->mm->mmap_sem);
@ -391,6 +398,9 @@ static unsigned long spufs_ps_nopfn(struct vm_area_struct *vma,
if (!ret)
spu_release(ctx);
refault:
put_spu_context(ctx);
return NOPFN_REFAULT;
}