Messages in this thread | | | Date | Thu, 1 Jun 2006 22:24:02 -0700 | From | Andrew Morton <> | Subject | Re: pci_walk_bus race condition |
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On Thu, 1 Jun 2006 22:11:41 -0700 Andrew Morton <akpm@osdl.org> wrote:
> On Fri, 02 Jun 2006 12:35:43 +0800 > "Zhang, Yanmin" <yanmin_zhang@linux.intel.com> wrote: > > > pci_walk_bus has a race with pci_destroy_dev. When cb is called > > in pci_walk_bus, pci_destroy_dev might unlink the dev pointed by next. > > Later on in the next loop, pointer next becomes NULL and cause > > kernel panic. > > > > Below patch against 2.6.17-rc4 fixes it by changing pci_bus_lock (spin_lock) > > to pci_bus_sem (rw_semaphore). > > How does s/spinlock/rwsem/ fix a race??
oic. "and hold the lock across the callback".
Is the ranking of pci_bus_sem and dev->dev.sem correct+consistent? It looks OK.
It might be worth making a not that the callback function cannot call any PCI layer function which takes pci_bus_sem - that'll casue a recursive down_read(), which is a nasty source of rare deadlocks.
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