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author | Peter Zijlstra <peterz@infradead.org> | 2018-06-05 16:53:34 +0200 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-06-28 21:07:55 +0900 |
commit | 5fd691afdf929061c391d897fa627822c3b2fd5a (patch) | |
tree | 005d50f2b2bc10ce6e6af270feaa1fc1efe77eae /include/linux/tty_ldisc.h | |
parent | 9d9398944488cd3a3e1e0912b26fbc4d5921e547 (diff) | |
download | lwn-5fd691afdf929061c391d897fa627822c3b2fd5a.tar.gz lwn-5fd691afdf929061c391d897fa627822c3b2fd5a.zip |
atomic/tty: Fix up atomic abuse in ldsem
Mark found ldsem_cmpxchg() needed an (atomic_long_t *) cast to keep
working after making the atomic_long interface type safe.
Needing casts is bad form, which made me look at the code. There are no
ld_semaphore::count users outside of these functions so there is no
reason why it can not be an atomic_long_t in the first place, obviating
the need for this cast.
That also ensures the loads use atomic_long_read(), which implies (at
least) READ_ONCE() in order to guarantee single-copy-atomic loads.
When using atomic_long_try_cmpxchg() the ldsem_cmpxchg() wrapper gets
very thin (the only difference is not changing *old on success, which
most callers don't seem to care about).
So rework the whole thing to use atomic_long_t and its accessors
directly.
While there, fixup all the horrible comment styles.
Cc: Peter Hurley <peter@hurleysoftware.com>
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/tty_ldisc.h')
-rw-r--r-- | include/linux/tty_ldisc.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h index 1ef64d4ad887..840894ca3fc0 100644 --- a/include/linux/tty_ldisc.h +++ b/include/linux/tty_ldisc.h @@ -119,13 +119,13 @@ #include <linux/fs.h> #include <linux/wait.h> - +#include <linux/atomic.h> /* * the semaphore definition */ struct ld_semaphore { - long count; + atomic_long_t count; raw_spinlock_t wait_lock; unsigned int wait_readers; struct list_head read_wait; |