Commit ef8ac063 authored Sep 12, 2014 by Rik van Riel Committed by Ingo Molnar Sep 19, 2014

seqlock: Add irqsave variant of read_seqbegin_or_lock()



There are cases where read_seqbegin_or_lock() needs to block irqs,
because the seqlock in question nests inside a lock that is also
be taken from irq context.

Add read_seqbegin_or_lock_irqsave() and done_seqretry_irqrestore(), which
are almost identical to read_seqbegin_or_lock() and done_seqretry().

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: prarit@redhat.com
Cc: oleg@redhat.com
Cc: sgruszka@redhat.com
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Link: http://lkml.kernel.org/r/1410527535-9814-2-git-send-email-riel@redhat.com


[ Improved the readability of the code a bit. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 2ed903c5

include/linux/seqlock.h

+19 −0

Original line number	Diff line number	Diff line
		@@ -456,4 +456,23 @@ read_sequnlock_excl_irqrestore(seqlock_t *sl, unsigned long flags)
		spin_unlock_irqrestore(&sl->lock, flags);
		}

		static inline unsigned long
		read_seqbegin_or_lock_irqsave(seqlock_t lock, int seq)
		{
		unsigned long flags = 0;

		if (!(seq & 1)) / Even */
		*seq = read_seqbegin(lock);
		else /* Odd */
		read_seqlock_excl_irqsave(lock, flags);

		return flags;
		}

		static inline void
		done_seqretry_irqrestore(seqlock_t *lock, int seq, unsigned long flags)
		{
		if (seq & 1)
		read_sequnlock_excl_irqrestore(lock, flags);
		}
		#endif /* __LINUX_SEQLOCK_H */

Admin message