• Thomas Huth's avatar
    powerpc/rtas: Introduce rtas_get_sensor_fast() for IRQ handlers · 5a03b287
    Thomas Huth authored
    commit 1c2cb594 upstream.
    
    The EPOW interrupt handler uses rtas_get_sensor(), which in turn
    uses rtas_busy_delay() to wait for RTAS becoming ready in case it
    is necessary. But rtas_busy_delay() is annotated with might_sleep()
    and thus may not be used by interrupts handlers like the EPOW handler!
    This leads to the following BUG when CONFIG_DEBUG_ATOMIC_SLEEP is
    enabled:
    
     BUG: sleeping function called from invalid context at arch/powerpc/kernel/rtas.c:496
     in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper/1
     CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.2.0-rc2-thuth #6
     Call Trace:
     [c00000007ffe7b90] [c000000000807670] dump_stack+0xa0/0xdc (unreliable)
     [c00000007ffe7bc0] [c0000000000e1f14] ___might_sleep+0x134/0x180
     [c00000007ffe7c20] [c00000000002aec0] rtas_busy_delay+0x30/0xd0
     [c00000007ffe7c50] [c00000000002bde4] rtas_get_sensor+0x74/0xe0
     [c00000007ffe7ce0] [c000000000083264] ras_epow_interrupt+0x44/0x450
     [c00000007ffe7d90] [c000000000120260] handle_irq_event_percpu+0xa0/0x300
     [c00000007ffe7e70] [c000000000120524] handle_irq_event+0x64/0xc0
     [c00000007ffe7eb0] [c000000000124dbc] handle_fasteoi_irq+0xec/0x260
     [c00000007ffe7ef0] [c00000000011f4f0] generic_handle_irq+0x50/0x80
     [c00000007ffe7f20] [c000000000010f3c] __do_irq+0x8c/0x200
     [c00000007ffe7f90] [c0000000000236cc] call_do_irq+0x14/0x24
     [c00000007e6f39e0] [c000000000011144] do_IRQ+0x94/0x110
     [c00000007e6f3a30] [c000000000002594] hardware_interrupt_common+0x114/0x180
    
    Fix this issue by introducing a new rtas_get_sensor_fast() function
    that does not use rtas_busy_delay() - and thus can only be used for
    sensors that do not cause a BUSY condition - known as "fast" sensors.
    
    The EPOW sensor is defined to be "fast" in sPAPR - mpe.
    
    Fixes: 587f83e8 ("powerpc/pseries: Use rtas_get_sensor in RAS code")
    Signed-off-by: default avatarThomas Huth <thuth@redhat.com>
    Reviewed-by: default avatarNathan Fontenot <nfont@linux.vnet.ibm.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
    5a03b287
rtas.c 28.4 KB