bnx2x: Revising locking scheme for MAC configuration
On very rare occasions, repeated load/unload stress test in the presence of our storage driver (bnx2i/bnx2fc) causes a kernel panic in bnx2x code (NULL pointer dereference). Stack traces indicate the issue happens during MAC configuration; thorough code review showed that indeed several races exist in which one thread can iterate over the list of configured MACs while another deletes entries from the same list. This patch adds a varient on the single-writer/Multiple-reader lock mechanism - It utilizes an already exsiting bottom-half lock, using it so that Whenever a writer is unable to continue due to the existence of another writer/reader, it pends its request for future deliverance. The writer / last readers will check for the existence of such requests and perform them instead of the original initiator. This prevents the writer from having to sleep while waiting for the lock to be accessible, which might cause deadlocks given the locks already held by the writer. Another result of this patch is that setting of Rx Mode is now made in sleepable context - Setting of Rx Mode is made under a bottom-half lock, which was always nontrivial for the bnx2x driver, as the HW/FW configuration requires wait for completions. Since sleep was impossible (due to the sleepless-context), various mechanisms were utilized to prevent the calling thread from sleep, but the truth was that when the caller thread (i.e, the one calling ndo_set_rx_mode()) returned, the Rx mode was still not set in HW/FW. bnx2x_set_rx_mode() will now overtly schedule for the Rx changes to be configured by the sp_rtnl_task which hold the RTNL lock and is sleepable context. Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com> Signed-off-by: Ariel Elior <ariele@broadcom.com> Signed-off-by: Eilon Greenstein <eilong@broadcom.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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