phylib: Fix deadlock on resume
Sometimes kernel hangs on resume with the following trace: ucc_geth e0102000.ucc: resume INFO: task bash:1764 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. bash D 0fecf43c 0 1764 1763 0x00000000 Call Trace: [cf9a7c10] [c0012868] ret_from_except+0x0/0x14 (unreliable) --- Exception: cf9a7ce0 at __switch_to+0x4c/0x6c LR = 0xcf9a7cc0 [cf9a7cd0] [c0008c14] __switch_to+0x4c/0x6c (unreliable) [cf9a7ce0] [c028bcfc] schedule+0x158/0x260 [cf9a7d10] [c028c720] __mutex_lock_slowpath+0x80/0xd8 [cf9a7d40] [c01cf388] phy_stop+0x20/0x70 [cf9a7d50] [c01d514c] ugeth_resume+0x6c/0x13c [...] Here is why. On suspend: - PM core starts suspending devices, ucc_geth_suspend gets called; - ucc_geth calls phy_stop() on suspend. Note that phy_stop() is mostly asynchronous so it doesn't block ucc_geth's suspend routine, it just sets PHY_HALTED state and disables PHY's interrupts; - Suddenly the state machine gets scheduled, it grabs the phydev->lock mutex and tries to process the PHY_HALTED state, so it calls phydev->adjust_link(phydev->attached_dev). In ucc_geth case adjust_link() calls msleep(), which reschedules the code flow back to PM core, which now finishes suspend and so we end up sleeping with phydev->lock mutex held. On resume: - PM core starts resuming devices (notice that nobody rescheduled the state machine yet, so the mutex is still held), the core calls ucc_geth's resume routine; - ucc_geth_resume restarts the PHY with phy_stop()/phy_start() sequence, and the phy_*() calls are trying to grab the phydev->lock mutex. Here comes the deadlock. This patch fixes the issue by stopping the state machine on suspend and starting it again on resume. Signed-off-by:Anton Vorontsov <avorontsov@ru.mvista.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
parent
7f9d3577