* [PATCH] ata: pata_it821x: Replace mdelay with usleep_range in it821x_firmware_command
@ 2018-01-25 10:32 Jia-Ju Bai
2018-01-25 15:31 ` Tejun Heo
0 siblings, 1 reply; 2+ messages in thread
From: Jia-Ju Bai @ 2018-01-25 10:32 UTC (permalink / raw)
To: b.zolnierkie, tj; +Cc: linux-ide, linux-kernel, Jia-Ju Bai
After checking all possible call chains to it821x_firmware_command here,
my tool finds that it821x_firmware_command
is never called in atomic context,
namely never in an interrupt handler or holding a spinlock.
And it821x_firmware_command calls kmalloc(GFP_KERNEL),
so it proves again that it821x_firmware_command
can call functions which can sleep.
Thus mdelay can be replaced with usleep_range to avoid busy wait.
This is found by a static analysis tool named DCNS written by myself.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
drivers/ata/pata_it821x.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/ata/pata_it821x.c b/drivers/ata/pata_it821x.c
index 7a21edf..8468b30 100644
--- a/drivers/ata/pata_it821x.c
+++ b/drivers/ata/pata_it821x.c
@@ -683,7 +683,7 @@ static u8 *it821x_firmware_command(struct ata_port *ap, u8 cmd, int len)
ioread16_rep(ap->ioaddr.data_addr, buf, len/2);
return (u8 *)buf;
}
- mdelay(1);
+ usleep_range(500, 1000);
}
kfree(buf);
printk(KERN_ERR "it821x_firmware_command: timeout\n");
--
1.7.9.5
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] ata: pata_it821x: Replace mdelay with usleep_range in it821x_firmware_command
2018-01-25 10:32 [PATCH] ata: pata_it821x: Replace mdelay with usleep_range in it821x_firmware_command Jia-Ju Bai
@ 2018-01-25 15:31 ` Tejun Heo
0 siblings, 0 replies; 2+ messages in thread
From: Tejun Heo @ 2018-01-25 15:31 UTC (permalink / raw)
To: Jia-Ju Bai; +Cc: b.zolnierkie, linux-ide, linux-kernel
On Thu, Jan 25, 2018 at 06:32:59PM +0800, Jia-Ju Bai wrote:
> After checking all possible call chains to it821x_firmware_command here,
> my tool finds that it821x_firmware_command
> is never called in atomic context,
> namely never in an interrupt handler or holding a spinlock.
> And it821x_firmware_command calls kmalloc(GFP_KERNEL),
> so it proves again that it821x_firmware_command
> can call functions which can sleep.
> Thus mdelay can be replaced with usleep_range to avoid busy wait.
>
> This is found by a static analysis tool named DCNS written by myself.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Applied to libata/for-4.16.
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 2+ messages in thread
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2018-01-25 10:32 [PATCH] ata: pata_it821x: Replace mdelay with usleep_range in it821x_firmware_command Jia-Ju Bai
2018-01-25 15:31 ` Tejun Heo
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