https://github.com/torvalds/linux
Revision eced1dfcfcf6b0a35e925d73916a9d8e36ab5457 authored by Peter Zijlstra on 28 August 2009, 15:10:47 UTC, committed by Ingo Molnar on 29 August 2009, 11:20:11 UTC
We have a race in the swcounter stuff where we can start counting a counter that has never been enabled, this leads to a /0 situation. The below avoids the /0 but doesn't close the race, this would need a new counter state. The race is due to perf_swcounter_is_counting() which cannot discern between disabled due to scheduled out, and disabled for any other reason. Such a crash has been seen by Ingo: [ 967.092372] divide error: 0000 [#1] SMP [ 967.096499] last sysfs file: /sys/devices/system/cpu/cpu15/cache/index2/shared_cpu_map [ 967.104846] CPU 5 [ 967.106965] Modules linked in: [ 967.110169] Pid: 3351, comm: hackbench Not tainted 2.6.31-rc8-tip-01158-gd940a54-dirty #1568 X8DTN [ 967.119456] RIP: 0010:[<ffffffff810c0aba>] [<ffffffff810c0aba>] perf_swcounter_ctx_event+0x127/0x1af [ 967.129137] RSP: 0018:ffff8801a95abd70 EFLAGS: 00010046 [ 967.134699] RAX: 0000000000000002 RBX: ffff8801bd645c00 RCX: 0000000000000002 [ 967.142162] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8801bd645d40 [ 967.149584] RBP: ffff8801a95abdb0 R08: 0000000000000001 R09: ffff8801a95abe00 [ 967.157042] R10: 0000000000000037 R11: ffff8801aa1245f8 R12: ffff8801a95abe00 [ 967.164481] R13: ffff8801a95abe00 R14: ffff8801aa1c0e78 R15: 0000000000000001 [ 967.171953] FS: 0000000000000000(0000) GS:ffffc90000a00000(0063) knlGS:00000000f7f486c0 [ 967.180406] CS: 0010 DS: 002b ES: 002b CR0: 000000008005003b [ 967.186374] CR2: 000000004822c0ac CR3: 00000001b19a2000 CR4: 00000000000006e0 [ 967.193770] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 967.201224] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 967.208692] Process hackbench (pid: 3351, threadinfo ffff8801a95aa000, task ffff8801a96b0000) [ 967.217607] Stack: [ 967.219711] 0000000000000000 0000000000000037 0000000200000001 ffffc90000a1107c [ 967.227296] <0> ffff8801a95abe00 0000000000000001 0000000000000001 0000000000000037 [ 967.235333] <0> ffff8801a95abdf0 ffffffff810c0c20 0000000200a14f30 ffff8801a95abe40 [ 967.243532] Call Trace: [ 967.246103] [<ffffffff810c0c20>] do_perf_swcounter_event+0xde/0xec [ 967.252635] [<ffffffff810c0ca7>] perf_tpcounter_event+0x79/0x7b [ 967.258957] [<ffffffff81037f73>] ftrace_profile_sched_switch+0xc0/0xcb [ 967.265791] [<ffffffff8155f22d>] schedule+0x429/0x4c4 [ 967.271156] [<ffffffff8100c01e>] int_careful+0xd/0x14 Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> LKML-Reference: <1251472247.17617.74.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
1 parent 6bb5634
Tip revision: eced1dfcfcf6b0a35e925d73916a9d8e36ab5457 authored by Peter Zijlstra on 28 August 2009, 15:10:47 UTC
perf_counter: Fix /0 bug in swcounters
perf_counter: Fix /0 bug in swcounters
Tip revision: eced1df
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arch | ||
block | ||
crypto | ||
drivers | ||
firmware | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.gitignore | -rw-r--r-- | 952 bytes |
.mailmap | -rw-r--r-- | 3.9 KB |
COPYING | -rw-r--r-- | 18.3 KB |
CREDITS | -rw-r--r-- | 91.8 KB |
Kbuild | -rw-r--r-- | 2.4 KB |
MAINTAINERS | -rw-r--r-- | 148.6 KB |
Makefile | -rw-r--r-- | 53.9 KB |
README | -rw-r--r-- | 17.0 KB |
REPORTING-BUGS | -rw-r--r-- | 3.3 KB |
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