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    Subject[PATCH 5.8 365/633] powerpc/tau: Convert from timer to workqueue
    Date
    From: Finn Thain <fthain@telegraphics.com.au>

    [ Upstream commit b1c6a0a10bfaf36ec82fde6f621da72407fa60a1 ]

    Since commit 19dbdcb8039cf ("smp: Warn on function calls from softirq
    context") the Thermal Assist Unit driver causes a warning like the
    following when CONFIG_SMP is enabled.

    ------------[ cut here ]------------
    WARNING: CPU: 0 PID: 0 at kernel/smp.c:428 smp_call_function_many_cond+0xf4/0x38c
    Modules linked in:
    CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.7.0-pmac #3
    NIP: c00b37a8 LR: c00b3abc CTR: c001218c
    REGS: c0799c60 TRAP: 0700 Not tainted (5.7.0-pmac)
    MSR: 00029032 <EE,ME,IR,DR,RI> CR: 42000224 XER: 00000000
    GPR00: c00b3abc c0799d18 c076e300 c079ef5c c0011fec 00000000 00000000 00000000
    GPR08: 00000100 00000100 00008000 ffffffff 42000224 00000000 c079d040 c079d044
    GPR16: 00000001 00000000 00000004 c0799da0 c079f054 c07a0000 c07a0000 00000000
    GPR24: c0011fec 00000000 c079ef5c c079ef5c 00000000 00000000 00000000 00000000
    NIP [c00b37a8] smp_call_function_many_cond+0xf4/0x38c
    LR [c00b3abc] on_each_cpu+0x38/0x68
    Call Trace:
    [c0799d18] [ffffffff] 0xffffffff (unreliable)
    [c0799d68] [c00b3abc] on_each_cpu+0x38/0x68
    [c0799d88] [c0096704] call_timer_fn.isra.26+0x20/0x7c
    [c0799d98] [c0096b40] run_timer_softirq+0x1d4/0x3fc
    [c0799df8] [c05b4368] __do_softirq+0x118/0x240
    [c0799e58] [c0039c44] irq_exit+0xc4/0xcc
    [c0799e68] [c000ade8] timer_interrupt+0x1b0/0x230
    [c0799ea8] [c0013520] ret_from_except+0x0/0x14
    --- interrupt: 901 at arch_cpu_idle+0x24/0x6c
    LR = arch_cpu_idle+0x24/0x6c
    [c0799f70] [00000001] 0x1 (unreliable)
    [c0799f80] [c0060990] do_idle+0xd8/0x17c
    [c0799fa0] [c0060ba8] cpu_startup_entry+0x24/0x28
    [c0799fb0] [c072d220] start_kernel+0x434/0x44c
    [c0799ff0] [00003860] 0x3860
    Instruction dump:
    8129f204 2f890000 40beff98 3d20c07a 8929eec4 2f890000 40beff88 0fe00000
    81220000 552805de 550802ef 4182ff84 <0fe00000> 3860ffff 7f65db78 7f44d378
    ---[ end trace 34a886e47819c2eb ]---

    Don't call on_each_cpu() from a timer callback, call it from a worker
    thread instead.

    Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
    Tested-by: Stan Johnson <userm57@yahoo.com>
    Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/bb61650bea4f4c91fb8e24b9a6f130a1438651a7.1599260540.git.fthain@telegraphics.com.au
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/kernel/tau_6xx.c | 38 +++++++++++++++++------------------
    1 file changed, 18 insertions(+), 20 deletions(-)

    diff --git a/arch/powerpc/kernel/tau_6xx.c b/arch/powerpc/kernel/tau_6xx.c
    index 976d5bc1b5176..268205cc347da 100644
    --- a/arch/powerpc/kernel/tau_6xx.c
    +++ b/arch/powerpc/kernel/tau_6xx.c
    @@ -13,13 +13,14 @@
    */

    #include <linux/errno.h>
    -#include <linux/jiffies.h>
    #include <linux/kernel.h>
    #include <linux/param.h>
    #include <linux/string.h>
    #include <linux/mm.h>
    #include <linux/interrupt.h>
    #include <linux/init.h>
    +#include <linux/delay.h>
    +#include <linux/workqueue.h>

    #include <asm/io.h>
    #include <asm/reg.h>
    @@ -39,8 +40,6 @@ static struct tau_temp
    unsigned char grew;
    } tau[NR_CPUS];

    -struct timer_list tau_timer;
    -
    #undef DEBUG

    /* TODO: put these in a /proc interface, with some sanity checks, and maybe
    @@ -50,7 +49,7 @@ struct timer_list tau_timer;
    #define step_size 2 /* step size when temp goes out of range */
    #define window_expand 1 /* expand the window by this much */
    /* configurable values for shrinking the window */
    -#define shrink_timer 2*HZ /* period between shrinking the window */
    +#define shrink_timer 2000 /* period between shrinking the window */
    #define min_window 2 /* minimum window size, degrees C */

    static void set_thresholds(unsigned long cpu)
    @@ -187,14 +186,18 @@ static void tau_timeout(void * info)
    local_irq_restore(flags);
    }

    -static void tau_timeout_smp(struct timer_list *unused)
    -{
    +static struct workqueue_struct *tau_workq;

    - /* schedule ourselves to be run again */
    - mod_timer(&tau_timer, jiffies + shrink_timer) ;
    +static void tau_work_func(struct work_struct *work)
    +{
    + msleep(shrink_timer);
    on_each_cpu(tau_timeout, NULL, 0);
    + /* schedule ourselves to be run again */
    + queue_work(tau_workq, work);
    }

    +DECLARE_WORK(tau_work, tau_work_func);
    +
    /*
    * setup the TAU
    *
    @@ -227,21 +230,16 @@ static int __init TAU_init(void)
    return 1;
    }

    -
    - /* first, set up the window shrinking timer */
    - timer_setup(&tau_timer, tau_timeout_smp, 0);
    - tau_timer.expires = jiffies + shrink_timer;
    - add_timer(&tau_timer);
    + tau_workq = alloc_workqueue("tau", WQ_UNBOUND, 1, 0);
    + if (!tau_workq)
    + return -ENOMEM;

    on_each_cpu(TAU_init_smp, NULL, 0);

    - printk("Thermal assist unit ");
    -#ifdef CONFIG_TAU_INT
    - printk("using interrupts, ");
    -#else
    - printk("using timers, ");
    -#endif
    - printk("shrink_timer: %d jiffies\n", shrink_timer);
    + queue_work(tau_workq, &tau_work);
    +
    + pr_info("Thermal assist unit using %s, shrink_timer: %d ms\n",
    + IS_ENABLED(CONFIG_TAU_INT) ? "interrupts" : "workqueue", shrink_timer);
    tau_initialized = 1;

    return 0;
    --
    2.25.1


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