Messages in this thread | | | Subject | Re: [PATCH net] page_pool: fix inconsistency for page_pool_ring_[un]lock() | From | Yunsheng Lin <> | Date | Sat, 27 May 2023 15:56:26 +0800 |
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On 2023/5/27 3:34, Jakub Kicinski wrote: > On Mon, 22 May 2023 11:17:14 +0800 Yunsheng Lin wrote: >> page_pool_ring_[un]lock() use in_softirq() to decide which >> spin lock variant to use, and when they are called in the >> context with in_softirq() being false, spin_lock_bh() is >> called in page_pool_ring_lock() while spin_unlock() is >> called in page_pool_ring_unlock(), because spin_lock_bh() >> has disabled the softirq in page_pool_ring_lock(), which >> causes inconsistency for spin lock pair calling. >> >> This patch fixes it by returning in_softirq state from >> page_pool_producer_lock(), and use it to decide which >> spin lock variant to use in page_pool_producer_unlock(). >> >> As pool->ring has both producer and consumer lock, so >> rename it to page_pool_producer_[un]lock() to reflect >> the actual usage. Also move them to page_pool.c as they >> are only used there, and remove the 'inline' as the >> compiler may have better idea to do inlining or not. >> >> Fixes: 7886244736a4 ("net: page_pool: Add bulk support for ptr_ring") >> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com> > > I just realized now while doing backports that the Fixes tag is > incorrect here. The correct Fixes tag is: > > Fixes: 542bcea4be86 ("net: page_pool: use in_softirq() instead") > > Before that we used in_serving_softirq() which was perfectly fine.
From the comment around in_serving_softirq() and in_softirq(), you are probably right as in_serving_softirq() is always false no matter if bh is enabled or disabled.
> This explains the major mystery of how such a serious bug would survive > for 10+ releases... it didn't, it wasn't there :) It only came in 6.3. > We can't change the tag now but at least the universe makes sense again.
Yes, it makes more sense now:)
> . >
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