[PATCH 5.9 445/757] powerpc/tau: Convert from timer to workqueue

Greg Kroah-Hartman
2020-10-27T16:20:46Z

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