Tejun Heo wrote:
Simon Farnsworth wrote:
Hello,
We're trying to consistently disable write caching on our systems (one
PATA disk on /dev/sda), by running the following command during boot:
hdparm -W0 /dev/sda
However, on some disks, we see a freeze of between 30 seconds and 2
minutes after issuing this command. How do we avoid this freeze? We're
happy to write our own userspace utility, or change the kernel.
We're using the pata_via driver, with a kernel that's the same code as
the Fedora 3189 kernel, but with CONFIG_DEBUG_STACKOVERFLOW set to n.
From a machine that's just done this freeze:
[--snip--]
BUG: warning at kernel/softirq.c:138/local_bh_enable() (Not tainted)
[<c042afff>] local_bh_enable+0x45/0x96
[<c0603cde>] cond_resched_softirq+0x2d/0x43
[<c05d55bf>] established_get_first+0x17/0xac
[<c05d8f93>] tcp_seq_next+0x71/0x86
[<c048c004>] seq_read+0x181/0x268
[<c048be83>] seq_read+0x0/0x268
[<c0476651>] vfs_read+0xab/0x15a
[<c0476fb7>] sys_read+0x41/0x67
[<c0404ecc>] syscall_call+0x7/0xb
=======================
Hmmmm.. This is the only suspicious looking part of the kernel log and
doesn't have too much to do with ATA freeze. 30sec - 2min delay sounds
awfully like something caused by ATA commands timing out but libata
always complains verbosely about those. Can you check dmesg again after
the freeze?
Regardless of that, the above WARN_ON_ONCE(irqs_disabled())
does indicate another bug in the kernel, that needs to be reported/tracked.
Who should he send that one to ?
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