• Signed-off-by: Darren Hart's avatar
    powerpc: Re-enable preemption before cpu_die() · a7c2bb82
    Signed-off-by: Darren Hart authored
    start_secondary() is called shortly after _start and also via
    
    cpu_idle()->cpu_die()->pseries_mach_cpu_die()
    
    start_secondary() expects a preempt_count() of 0. pseries_mach_cpu_die() is
    called via the cpu_idle() routine with preemption disabled, resulting in the
    following repeating message during rapid cpu offline/online tests
    with CONFIG_PREEMPT=y:
    
    BUG: scheduling while atomic: swapper/0/0x00000002
    Modules linked in: autofs4 binfmt_misc dm_mirror dm_region_hash dm_log [last unloaded: scsi_wait_scan]
    Call Trace:
    [c00000010e7079c0] [c0000000000133ec] .show_stack+0xd8/0x218 (unreliable)
    [c00000010e707aa0] [c0000000006a47f0] .dump_stack+0x28/0x3c
    [c00000010e707b20] [c00000000006e7a4] .__schedule_bug+0x7c/0x9c
    [c00000010e707bb0] [c000000000699d9c] .schedule+0x104/0x800
    [c00000010e707cd0] [c000000000015b24] .cpu_idle+0x1c4/0x1d8
    [c00000010e707d70] [c0000000006aa1b4] .start_secondary+0x398/0x3d4
    [c00000010e707e30] [c000000000008278] .start_secondary_resume+0x10/0x14
    
    Move the cpu_die() call inside the existing preemption enabled block of
    cpu_idle(). This is safe as the idle task is affined to a single CPU so the
    debug_smp_processor_id() tests (from cpu_should_die()) won't trigger as we are
    in a "migration disabled" region.
    Signed-off-by: default avatarDarren Hart <dvhltc@us.ibm.com>
    Acked-by: default avatarWill Schmidt <will_schmidt@vnet.ibm.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Nathan Fontenot <nfont@austin.ibm.com>
    Cc: Robert Jennings <rcj@linux.vnet.ibm.com>
    Cc: Brian King <brking@linux.vnet.ibm.com>
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    a7c2bb82
idle.c 2.99 KB