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Subjectsoftirq.c BUG's out
I tried to run tiobench on 2.5.32 on my machine, and got this:

Program received signal SIGTRAP, Trace/breakpoint trap.
tasklet_hi_action (a=0xc032fd60) at softirq.c:230
230 softirq.c: No such file or directory.
in softirq.c
(gdb) bt
#0 tasklet_hi_action (a=0xc032fd60) at softirq.c:230
#1 0xc011f3b2 in do_softirq () at softirq.c:89
#2 0xc0109bee in do_IRQ (regs=
{ebx = -1070398784, ecx = -463010764, edx = -511893504, esi = -608242656,
edi = -768991232, ebp = -511885904, eax = -1026729084, xds = 104, xes = -5119015
92, orig_eax = -256, eip = -1072436501, xcs = 96, eflags = 582, esp = -144631436
, xss = -608242656}) at irq.c:392
#3 0xc0108224 in common_interrupt () at process.c:982
#4 0xc013e999 in blk_queue_bounce (q=0xf790501c, bio_orig=0xe17d3e2c)
at /mnt/b/2.5.32/linux-2.5.32/include/asm/highmem.h:61
#5 0xc01db7f8 in __make_request (q=0xf790501c, bio=0xdbbef420)
at ll_rw_blk.c:1481
#6 0xc01dbd2f in generic_make_request (bio=0xdbbef420) at ll_rw_blk.c:1714
#7 0xc01dbdac in submit_bio (rw=1, bio=0xdbbef420) at ll_rw_blk.c:1760
#8 0xc01605d1 in mpage_bio_submit (rw=1, bio=0xdbbef420) at mpage.c:83
#9 0xc0160f54 in mpage_writepages (mapping=0xf71c39fc, nr_to_write=0x0,
get_block=0xc0173090 <ext2_get_block>) at mpage.c:434
#10 0xc01734f0 in ext2_writepages (mapping=0xf71c39fc, nr_to_write=0x0)
at inode.c:636
#11 0xc014060a in do_writepages (mapping=0xf71c39fc, nr_to_write=0x0)
at page-writeback.c:367
#12 0xc012f82a in filemap_fdatawrite (mapping=0xf71c39fc) at filemap.c:484
#13 0xc0144935 in sys_fsync (fd=52) at buffer.c:311
#14 0xc01078df in syscall_call () at process.c:982

Following some suggestions from akpm (save/restore flags and check the
bit before fiddling with the list below), and taking a small bit of
initiative of my own (removing the BUG check entirely and just assuming
someone else handled it -- AFAICT it's legitimate for this happen) I got
the following results instead of oopsing for the first time on 2.5 ever:


tiobench on disk 1:
Sequential Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 20.79 283.4% 22.998 111635.79 0.16956 0.02403 7

Random Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 18.66 346.9% 0.620 137.95 0.00000 0.00000 5

Sequential Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 3.76 52.42% 53.414 490850.36 0.17262 0.04263 7

Random Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 0.07 15.58% 200.620 58083.14 3.67188 0.07812 0


tiobench on disk 2:
Sequential Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 34.08 391.4% 14.576 74595.64 0.07753 0.02327 9

Random Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 4.41 40.39% 0.272 6.19 0.00000 0.00000 11

Sequential Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 3.24 39.10% 78.737 538753.18 0.08297 0.06924 8

Random Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 0.15 24.27% 44.161 4504.39 1.01562 0.00000 1


tiobench on disk 3:
Sequential Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 66.00 1023.% 9.294 25761.69 0.15011 0.01125 6

Random Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 2.38 28.99% 0.655 477.21 0.00000 0.00000 8

Sequential Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 3.67 58.33% 7.929 25735.00 0.08078 0.00038 6

Random Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 0.09 14.44% 66.025 21296.61 1.38021 0.02604 1


tiobench on disk 4:
Sequential Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 28.86 297.1% 18.640 104797.43 0.11721 0.02508 10

Random Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 77.29 1243.% 0.390 12.12 0.00000 0.00000 6

Sequential Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 3.34 37.64% 82.880 518269.40 0.07524 0.06428 9

Random Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- -----
2.5.32-3 4096 4096 256 0.09 23.59% 37.670 5785.26 0.44271 0.00000 0


Cheers,
Bill


--- linux-2.5.32-virgin/kernel/softirq.c 2002-08-27 12:26:37.000000000 -0700
+++ linux-2.5.32/kernel/softirq.c 2002-08-27 18:12:30.000000000 -0700
@@ -179,11 +179,12 @@
static void tasklet_action(struct softirq_action *a)
{
struct tasklet_struct *list;
+ unsigned long flags;

- local_irq_disable();
+ local_irq_save(flags);
list = __get_cpu_var(tasklet_vec).list;
__get_cpu_var(tasklet_vec).list = NULL;
- local_irq_enable();
+ local_irq_restore(flags);

while (list) {
struct tasklet_struct *t = list;
@@ -192,31 +193,34 @@

if (tasklet_trylock(t)) {
if (!atomic_read(&t->count)) {
- if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
- BUG();
- t->func(t->data);
- tasklet_unlock(t);
- continue;
+ if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
+ t->func(t->data);
+ tasklet_unlock(t);
+ continue;
+ }
}
tasklet_unlock(t);
}

- local_irq_disable();
- t->next = __get_cpu_var(tasklet_vec).list;
- __get_cpu_var(tasklet_vec).list = t;
- __cpu_raise_softirq(smp_processor_id(), TASKLET_SOFTIRQ);
- local_irq_enable();
+ local_irq_save(flags);
+ if (test_bit(TASKLET_STATE_SCHED, &t->state)) {
+ t->next = __get_cpu_var(tasklet_vec).list;
+ __get_cpu_var(tasklet_vec).list = t;
+ __cpu_raise_softirq(smp_processor_id(), TASKLET_SOFTIRQ);
+ }
+ local_irq_restore(flags);
}
}

static void tasklet_hi_action(struct softirq_action *a)
{
struct tasklet_struct *list;
+ unsigned long flags;

- local_irq_disable();
+ local_irq_save(flags);
list = __get_cpu_var(tasklet_hi_vec).list;
__get_cpu_var(tasklet_hi_vec).list = NULL;
- local_irq_enable();
+ local_irq_restore(flags);

while (list) {
struct tasklet_struct *t = list;
@@ -225,20 +229,23 @@

if (tasklet_trylock(t)) {
if (!atomic_read(&t->count)) {
- if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
- BUG();
- t->func(t->data);
- tasklet_unlock(t);
- continue;
+ if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
+
+ t->func(t->data);
+ tasklet_unlock(t);
+ continue;
+ }
}
tasklet_unlock(t);
}

- local_irq_disable();
- t->next = __get_cpu_var(tasklet_hi_vec).list;
- __get_cpu_var(tasklet_hi_vec).list = t;
- __cpu_raise_softirq(smp_processor_id(), HI_SOFTIRQ);
- local_irq_enable();
+ local_irq_save(flags);
+ if (test_bit(TASKLET_STATE_SCHED, &t->state)) {
+ t->next = __get_cpu_var(tasklet_hi_vec).list;
+ __get_cpu_var(tasklet_hi_vec).list = t;
+ __cpu_raise_softirq(smp_processor_id(), HI_SOFTIRQ);
+ }
+ local_irq_restore(flags);
}
}

-
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