Commit 7f5a8ba6 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky

[S390] No more 4kb stacks.

We got a stack overflow with a small stack configuration on a 32 bit
system. It just looks like as 4kb isn't enough and too dangerous.
So lets get rid of 4kb stacks on 32 bit.

But one thing I completely dislike about the call trace below is that
just for debugging or tracing purposes sprintf gets called (cio_start_key):

	/* process condition code */
	sprintf(dbf_txt, "ccode:%d", ccode);
	CIO_TRACE_EVENT(4, dbf_txt);

But maybe its just me who thinks that this could be done better.

    <4>Kernel stack overflow.
    <4>Modules linked in: dm_multipath sunrpc bonding qeth_l2 dm_mod qeth ccwgroup vmur
    <4>CPU: 1 Not tainted 2.6.27-30.x.20081015-s390default #1
    <4>Process httpd (pid: 3807, task: 20ae2df8, ksp: 1666fb78)
    <4>Krnl PSW : 040c0000 8027098a (number+0xe/0x348)
    <4>           R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:0 CC:0 PM:0
    <4>Krnl GPRS: 00d43318 0027097c 1666f277 9666f270
    <4>           00000000 00000000 0000000a ffffffff
    <4>           9666f270 1666f228 1666f277 1666f098
    <4>           00000002 80270982 80271016 1666f098
    <4>Krnl Code: 8027097e: f0340dd0a7f1	srp	3536(4,%r0),2033(%r10),4
    <4>           80270984: 0f00		clcl	%r0,%r0
    <4>           80270986: a7840001		brc	8,80270988
    <4>          >8027098a: 18ef		lr	%r14,%r15
    <4>           8027098c: a7faff68		ahi	%r15,-152
    <4>           80270990: 18bf		lr	%r11,%r15
    <4>           80270992: 18a2		lr	%r10,%r2
    <4>           80270994: 1893		lr	%r9,%r3

Modified calltrace with annotated stackframe size of each function:

stackframe size
    |
 0 304 vsnprintf+850 [0x271016]
 1  72 sprintf+74 [0x271522]
 2  56 cio_start_key+262 [0x2d4c16]
 3  56 ccw_device_start_key+222 [0x2dfe92]
 4  56 ccw_device_start+40 [0x2dff28]
 5  48 raw3215_start_io+104 [0x30b0f8]
 6  56 raw3215_write+494 [0x30ba0a]
 7  40 con3215_write+68 [0x30bafc]
 8  40 __call_console_drivers+146 [0x12b0fa]
 9  32 _call_console_drivers+102 [0x12b192]
10  64 release_console_sem+268 [0x12b614]
11 168 vprintk+462 [0x12bca6]
12  72 printk+68 [0x12bfd0]
13 256 __print_symbol+50 [0x15a882]
14  56 __show_trace+162 [0x103d06]
15  32 show_trace+224 [0x103e70]
16  48 show_stack+152 [0x103f20]
17  56 dump_stack+126 [0x104612]
18  96 __alloc_pages_internal+592 [0x175004]
19  80 cache_alloc_refill+776 [0x196f3c]
20  40 __kmalloc+258 [0x1972ae]
21  40 __alloc_skb+94 [0x328086]
22  32 pskb_copy+50 [0x328252]
23  32 skb_realloc_headroom+110 [0x328a72]
24 104 qeth_l2_hard_start_xmit+378 [0x7803bfde]
25  56 dev_hard_start_xmit+450 [0x32ef6e]
26  56 __qdisc_run+390 [0x3425d6]
27  48 dev_queue_xmit+410 [0x331e06]
28  40 ip_finish_output+308 [0x354ac8]
29  56 ip_output+218 [0x355b6e]
30  24 ip_local_out+56 [0x354584]
31 120 ip_queue_xmit+300 [0x355cec]
32  96 tcp_transmit_skb+812 [0x367da8]
33  40 tcp_push_one+158 [0x369fda]
34 112 tcp_sendmsg+852 [0x35d5a0]
35 240 sock_sendmsg+164 [0x32035c]
36  56 kernel_sendmsg+86 [0x32064a]
37  88 sock_no_sendpage+98 [0x322b22]
38 104 tcp_sendpage+70 [0x35cc1e]
39  48 sock_sendpage+74 [0x31eb66]
40  64 pipe_to_sendpage+102 [0x1c4b2e]
41  64 __splice_from_pipe+120 [0x1c5340]
42  72 splice_from_pipe+90 [0x1c57e6]
43  56 generic_splice_sendpage+38 [0x1c5832]
44  48 do_splice_from+104 [0x1c4c38]
45  48 direct_splice_actor+52 [0x1c4c88]
46  80 splice_direct_to_actor+180 [0x1c4f80]
47  72 do_splice_direct+70 [0x1c5112]
48  64 do_sendfile+360 [0x19de18]
49  72 sys_sendfile64+126 [0x19df32]
50 336 sysc_do_restart+18 [0x111a1a]
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 46e7951f
......@@ -241,19 +241,17 @@ config PACK_STACK
Say Y if you are unsure.
config SMALL_STACK
bool "Use 4kb/8kb for kernel stack instead of 8kb/16kb"
depends on PACK_STACK && !LOCKDEP
bool "Use 8kb for kernel stack instead of 16kb"
depends on PACK_STACK && 64BIT && !LOCKDEP
help
If you say Y here and the compiler supports the -mkernel-backchain
option the kernel will use a smaller kernel stack size. For 31 bit
the reduced size is 4kb instead of 8kb and for 64 bit it is 8kb
instead of 16kb. This allows to run more thread on a system and
reduces the pressure on the memory management for higher order
page allocations.
option the kernel will use a smaller kernel stack size. The reduced
size is 8kb instead of 16kb. This allows to run more threads on a
system and reduces the pressure on the memory management for higher
order page allocations.
Say N if you are unsure.
config CHECK_STACK
bool "Detect kernel stack overflow"
help
......
......@@ -15,13 +15,8 @@
* Size of kernel stack for each process
*/
#ifndef __s390x__
#ifndef __SMALL_STACK
#define THREAD_ORDER 1
#define ASYNC_ORDER 1
#else
#define THREAD_ORDER 0
#define ASYNC_ORDER 0
#endif
#else /* __s390x__ */
#ifndef __SMALL_STACK
#define THREAD_ORDER 2
......
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