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author | Jonathan Corbet <corbet@lwn.net> | 2009-02-01 14:26:59 -0700 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2009-03-16 08:32:27 -0600 |
commit | 76398425bb06b07cc3a3b1ce169c67dc9d6874ed (patch) | |
tree | e6e1800edda88b5592617a950daacf2199587a33 /net | |
parent | db1dd4d376134eba0e08af523b61cc566a4ea1cd (diff) | |
download | op-kernel-dev-76398425bb06b07cc3a3b1ce169c67dc9d6874ed.zip op-kernel-dev-76398425bb06b07cc3a3b1ce169c67dc9d6874ed.tar.gz |
Move FASYNC bit handling to f_op->fasync()
Removing the BKL from FASYNC handling ran into the challenge of keeping the
setting of the FASYNC bit in filp->f_flags atomic with regard to calls to
the underlying fasync() function. Andi Kleen suggested moving the handling
of that bit into fasync(); this patch does exactly that. As a result, we
have a couple of internal API changes: fasync() must now manage the FASYNC
bit, and it will be called without the BKL held.
As it happens, every fasync() implementation in the kernel with one
exception calls fasync_helper(). So, if we make fasync_helper() set the
FASYNC bit, we can avoid making any changes to the other fasync()
functions - as long as those functions, themselves, have proper locking.
Most fasync() implementations do nothing but call fasync_helper() - which
has its own lock - so they are easily verified as correct. The BKL had
already been pushed down into the rest.
The networking code has its own version of fasync_helper(), so that code
has been augmented with explicit FASYNC bit handling.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Miller <davem@davemloft.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'net')
-rw-r--r-- | net/socket.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/net/socket.c b/net/socket.c index 35dd737..0f75746 100644 --- a/net/socket.c +++ b/net/socket.c @@ -1030,6 +1030,13 @@ static int sock_fasync(int fd, struct file *filp, int on) lock_sock(sk); + spin_lock(&filp->f_lock); + if (on) + filp->f_flags |= FASYNC; + else + filp->f_flags &= ~FASYNC; + spin_unlock(&filp->f_lock); + prev = &(sock->fasync_list); for (fa = *prev; fa != NULL; prev = &fa->fa_next, fa = *prev) |