From: venkatram867@gmail.com (Venkatram Tummala)
To: kernelnewbies@lists.kernelnewbies.org
Subject: [virtual memory] page_table_lock & mmap_sem
Date: Tue, 29 Mar 2011 15:30:26 -0700 [thread overview]
Message-ID: <AANLkTimnyMAqrHpnx_7vBmcLruDYpGDw2axf-iQo6g8G@mail.gmail.com> (raw)
Hi,
Why do we need both page_table_lock & mmap_sem in the kernel. Why isn't
mmap_sem good enough for serialization. As far as i see it, all attempts to
change the page table hierarchy in the kernel is done after holding the
write lock on mmap_sem. As we are already holding the write lock, we do we
need an extra page_table_lock (spinlock) ? Are there any code paths in the
kernel which attempt to modify the page table hierarchy without holding the
write lock on mmap_sem ?
page_table_lock is a finer grained lock than mmap_sem but page_table_lock is
only taken after holding a write lock on mmap_sem (as far as i can tell).
What is the reasoning behind having an extra spinlock?
Thanks.
Venkatram Tummala
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Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-29 22:30 Venkatram Tummala [this message]
2011-03-30 3:58 ` [virtual memory] page_table_lock & mmap_sem sk.syed2
2011-03-31 15:14 ` Rik van Riel
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