Message ID | aa8dd4f5b50686871c9d3a1c27337006b1c9eea9.1427200114.git.jstancek@redhat.com (mailing list archive) |
---|---|
State | Accepted |
Commit | 68de8867ea5d99127e836c23f6bccf4d44859623 |
Delegated to: | Michael Ellerman |
Headers | show |
On Tue, 2015-24-03 at 12:33:22 UTC, Jan Stancek wrote: > One path in power_pmu_event_init() calls get_cpu_var(), but is > missing matching call to put_cpu_var(), which causes preemption > imbalance and crash in user-space: > > Page fault in user mode with in_atomic() = 1 mm = c000001fefa5a280 > NIP = 3fff9bf2cae0 MSR = 900000014280f032 > Oops: Weird page fault, sig: 11 [#23] <snip> Thanks. But I don't see this. I guess you have CONFIG_PREEMPT enabled? cheers
----- Original Message ----- > From: "Michael Ellerman" <mpe@ellerman.id.au> > To: "Jan Stancek" <jstancek@redhat.com>, linuxppc-dev@lists.ozlabs.org > Cc: linux-kernel@vger.kernel.org, paulus@samba.org, anton@samba.org, tj@kernel.org, cl@linux.com, jolsa@redhat.com, > jstancek@redhat.com, joel@jms.id.au > Sent: Wednesday, 25 March, 2015 6:25:09 AM > Subject: Re: powerpc/perf: add missing put_cpu_var in power_pmu_event_init > > On Tue, 2015-24-03 at 12:33:22 UTC, Jan Stancek wrote: > > One path in power_pmu_event_init() calls get_cpu_var(), but is > > missing matching call to put_cpu_var(), which causes preemption > > imbalance and crash in user-space: > > > > Page fault in user mode with in_atomic() = 1 mm = c000001fefa5a280 > > NIP = 3fff9bf2cae0 MSR = 900000014280f032 > > Oops: Weird page fault, sig: 11 [#23] > > <snip> > > Thanks. But I don't see this. I guess you have CONFIG_PREEMPT enabled? Hi, CONFIG_PREEMPT_NOTIFIERS=y # CONFIG_PREEMPT_NONE is not set CONFIG_PREEMPT_VOLUNTARY=y # CONFIG_PREEMPT is not set CONFIG_PREEMPT_COUNT=y but I think the difference comes from: CONFIG_DEBUG_ATOMIC_SLEEP=y I did following: - took the default config from RHEL7.1 kernel - ran 'make oldnoconfig'. - reproducer didn't trigger anything - then I added "CONFIG_DEBUG_ATOMIC_SLEEP=y" - this time reproducer triggered a panic (3 out of 3 attempts) Here's config from panic-ing kernel: http://fpaste.org/202543/ [ 133.957305] Page fault in user mode with in_atomic() = 1 mm = c000000005fc7e80 [ 133.957399] NIP = 3fff9be0cae0 MSR = 900000014280f032 [ 133.957405] Oops: Weird page fault, sig: 11 [#1] [ 133.957409] SMP NR_CPUS=2048 NUMA PowerNV [ 133.957414] Modules linked in: ses enclosure shpchp uio_pdrv_genirq powernv_rng uio xfs libcrc32c sr_mod sd_mod cdrom ipr libata tg3 ptp pps_core dm_mirror dm_region_hash dm_log dm_mod [ 133.957638] CPU: 16 PID: 6035 Comm: a.out Not tainted 4.0.0-rc5+ #4 [ 133.957693] task: c000000fea44b640 ti: c000000fea5e4000 task.ti: c000000fea5e4000 [ 133.957759] NIP: 00003fff9be0cae0 LR: 00003fff9bdc4898 CTR: 00003fff9be0cae0 [ 133.957825] REGS: c000000fea5e7ea0 TRAP: 0401 Not tainted (4.0.0-rc5+) [ 133.957880] MSR: 900000014280f032 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI> CR: 22000028 XER: 00000000 [ 133.958079] CFAR: 00003fff9bdc4894 SOFTE: 1 GPR00: 00003fff9bdc494c 00003ffff1fef3e0 00003fff9bf64410 0000000010020068 GPR04: 0000000000000000 0000000000000002 0000000000000008 0000000000000001 GPR08: 0000000000000001 00003fff9bf54a30 00003fff9be0cae0 00003fff9be0cd70 GPR12: 0000000052000022 00003fff9bfeb700 [ 133.958485] NIP [00003fff9be0cae0] 0x3fff9be0cae0 [ 133.958530] LR [00003fff9bdc4898] 0x3fff9bdc4898 [ 133.958574] Call Trace: [ 133.958597] ---[ end trace 56ec543903422cd9 ]--- [ 133.958642] [ 135.958709] Kernel panic - not syncing: Fatal exception [ 135.958863] Rebooting in 10 seconds.. [ 145.970348] BUG: sleeping function called from invalid context at kernel/irq/manage.c:104 [ 145.970453] in_atomic(): 1, irqs_disabled(): 1, pid: 6035, name: a.out [ 145.970515] CPU: 16 PID: 6035 Comm: a.out Tainted: G D 4.0.0-rc5+ #4 [ 145.970588] Call Trace: [ 145.970618] [c000000fea5e76d0] [c0000000007c2090] .dump_stack+0x98/0xd4 (unreliable) [ 145.970707] [c000000fea5e7750] [c0000000000d5fe4] .___might_sleep+0x124/0x170 [ 145.970782] [c000000fea5e77c0] [c000000000112860] .synchronize_irq+0x40/0xe0 [ 145.970857] [c000000fea5e7880] [c000000000112fa8] .__free_irq+0xf8/0x2b0 [ 145.970931] [c000000fea5e7920] [c000000000113258] .free_irq+0x78/0x100 [ 145.971007] [c000000fea5e79b0] [c000000000067ae8] .opal_shutdown+0x88/0x120 [ 145.971081] [c000000fea5e7a40] [c000000000063e88] .pnv_shutdown+0x18/0x30 [ 145.971157] [c000000fea5e7ab0] [c000000000020c98] .machine_shutdown+0x38/0x50 [ 145.971231] [c000000fea5e7b20] [c000000000020d24] .machine_restart+0x14/0x70 [ 145.971307] [c000000fea5e7ba0] [c0000000000cdc10] .emergency_restart+0x20/0x40 [ 145.971393] [c000000fea5e7c10] [c0000000007bb0a4] .panic+0x224/0x2a4 [ 145.971468] [c000000fea5e7cb0] [c00000000001e1fc] .die+0x43c/0x450 [ 145.971543] [c000000fea5e7d60] [c0000000007b62c4] .do_page_fault+0x2d4/0x8f0 [ 145.971618] [c000000fea5e7e30] [c000000000008664] handle_page_fault+0x10/0x30 Regards, Jan
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c index 7c4f669..b101c0b 100644 --- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -1832,8 +1832,10 @@ static int power_pmu_event_init(struct perf_event *event) cpuhw->bhrb_filter = ppmu->bhrb_filter_map( event->attr.branch_sample_type); - if(cpuhw->bhrb_filter == -1) + if (cpuhw->bhrb_filter == -1) { + put_cpu_var(cpu_hw_events); return -EOPNOTSUPP; + } } put_cpu_var(cpu_hw_events);
One path in power_pmu_event_init() calls get_cpu_var(), but is missing matching call to put_cpu_var(), which causes preemption imbalance and crash in user-space: Page fault in user mode with in_atomic() = 1 mm = c000001fefa5a280 NIP = 3fff9bf2cae0 MSR = 900000014280f032 Oops: Weird page fault, sig: 11 [#23] SMP NR_CPUS=2048 NUMA PowerNV Modules linked in: <snip> CPU: 43 PID: 10285 Comm: a.out Tainted: G D 4.0.0-rc5+ #1 task: c000001fe82c9200 ti: c000001fe835c000 task.ti: c000001fe835c000 NIP: 00003fff9bf2cae0 LR: 00003fff9bee4898 CTR: 00003fff9bf2cae0 REGS: c000001fe835fea0 TRAP: 0401 Tainted: G D (4.0.0-rc5+) MSR: 900000014280f032 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI> CR: 22000028 XER: 00000000 CFAR: 00003fff9bee4894 SOFTE: 1 GPR00: 00003fff9bee494c 00003fffe01c2ee0 00003fff9c084410 0000000010020068 GPR04: 0000000000000000 0000000000000002 0000000000000008 0000000000000001 GPR08: 0000000000000001 00003fff9c074a30 00003fff9bf2cae0 00003fff9bf2cd70 GPR12: 0000000052000022 00003fff9c10b700 NIP [00003fff9bf2cae0] 0x3fff9bf2cae0 LR [00003fff9bee4898] 0x3fff9bee4898 Call Trace: ---[ end trace 5d3d952b5d4185d4 ]--- BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:41 in_atomic(): 1, irqs_disabled(): 0, pid: 10285, name: a.out INFO: lockdep is turned off. CPU: 43 PID: 10285 Comm: a.out Tainted: G D 4.0.0-rc5+ #1 Call Trace: [c000001fe835f990] [c00000000089c014] .dump_stack+0x98/0xd4 (unreliable) [c000001fe835fa10] [c0000000000e4138] .___might_sleep+0x1d8/0x2e0 [c000001fe835faa0] [c000000000888da8] .down_read+0x38/0x110 [c000001fe835fb30] [c0000000000bf2f4] .exit_signals+0x24/0x160 [c000001fe835fbc0] [c0000000000abde0] .do_exit+0xd0/0xe70 [c000001fe835fcb0] [c00000000001f4c4] .die+0x304/0x450 [c000001fe835fd60] [c00000000088e1f4] .do_page_fault+0x2d4/0x900 [c000001fe835fe30] [c000000000008664] handle_page_fault+0x10/0x30 note: a.out[10285] exited with preempt_count 1 Reproducer: #include <stdio.h> #include <unistd.h> #include <syscall.h> #include <sys/types.h> #include <sys/stat.h> #include <linux/perf_event.h> #include <linux/hw_breakpoint.h> static struct perf_event_attr event = { .type = PERF_TYPE_RAW, .size = sizeof(struct perf_event_attr), .sample_type = PERF_SAMPLE_BRANCH_STACK, .branch_sample_type = PERF_SAMPLE_BRANCH_ANY_RETURN, }; int main() { syscall(__NR_perf_event_open, &event, 0, -1, -1, 0); } Signed-off-by: Jan Stancek <jstancek@redhat.com> --- arch/powerpc/perf/core-book3s.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-)