Bug 204273
| Summary: | panic: [pmc,4204] cpu 0 didn't find a sample to collect | ||
|---|---|---|---|
| Product: | Base System | Reporter: | Ed Maste <emaste> |
| Component: | kern | Assignee: | Andrew Turner <Andrew> |
| Status: | Closed FIXED | ||
| Severity: | Affects Only Me | CC: | Andrew, br |
| Priority: | --- | ||
| Version: | CURRENT | ||
| Hardware: | arm64 | ||
| OS: | Any | ||
| URL: | https://reviews.freebsd.org/D6581 | ||
| Bug Depends on: | |||
| Bug Blocks: | 203349 | ||
As a workaround I commented the KASSERT out with no ill effects. A commit references this bug: Author: andrew Date: Sat May 28 13:05:40 UTC 2016 New revision: 300902 URL: https://svnweb.freebsd.org/changeset/base/300902 Log: Don't panic in hwpmc when stopping sampling. When hwpmc stops sampling it will set the pm_state to something other than PMC_STATE_RUNNING. This means the following sequence can happen: CPU 0: Enter the interrupt handler CPU 0: Set the thread TDP_CALLCHAIN pflag CPU 1: Stop sampling CPU 0: Call pmc_process_samples, sampling is stopped so clears ps_nsamples CPU 0: Finishes interrupt processing with the TDP_CALLCHAIN flag set CPU 0: Call pmc_capture_user_callchain to capture the user call chain CPU 0: Find all the pmc sample are free so no call chains need to be captured CPU 0: KASSERT because of this This fixes the issue by checking if any of the samples have been stopped and including this in te KASSERT. PR: 204273 Reviewed by: bz, gnn Obtained from: ABT Systems Ltd Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D6581 Changes: head/sys/dev/hwpmc/hwpmc_mod.c |
pmccontrol -L - see the things pmcstat -S CPU_CYCLES -T -w 1 .. and panic. panic: [pmc,4204] cpu 0 didn't find a sample to collect [71/1850] cpuid = 0 KDB: stack backtrace: db_trace_self() at db_trace_self_wrapper+0x28 pc = 0xffffff80004d6254 lr = 0xffffff800006d888 sp = 0xffffff87cc2156f0 fp = 0xffffff87cc215810 db_trace_self_wrapper() at vpanic+0x170 pc = 0xffffff800006d888 lr = 0xffffff800025abd0 sp = 0xffffff87cc215820 fp = 0xffffff87cc2158a0 vpanic() at kassert_panic+0x160 pc = 0xffffff800025abd0 lr = 0xffffff800025aa5c sp = 0xffffff87cc2158b0 fp = 0xffffff87cc215970 kassert_panic() at pmc_capture_user_callchain+0x134 pc = 0xffffff800025aa5c lr = 0xffffff8047e2b1e8 sp = 0xffffff87cc215980 fp = 0xffffff87cc2159d0 pmc_capture_user_callchain() at pmc_hook_handler+0x4a0 pc = 0xffffff8047e2b1e8 lr = 0xffffff8047e296e8 sp = 0xffffff87cc2159e0 fp = 0xffffff87cc215a60 pmc_hook_handler() at ast+0x14cCYCLES -T -w 1 [48/1850] pc = 0xffffff8047e296e8 lr = 0xffffff80002a5c20 sp = 0xffffff87cc215a70 fp = 0xffffff87cc215aa0 ast() at handle_el0_irq+0x88 pc = 0xffffff80002a5c20 lr = 0xffffff80004d72e8 sp = 0xffffff87cc215ab0 fp = 0x0000007fffff40e0 KDB: enter: panic [ thread pid 3341 tid 100475 ] Stopped at kdb_enter+0x40: db> call doadump Dumping 3761 out of 131034 MB:..1%(ada0:ahcich0:0:0:0): WRITE_DMA. ACB: ca 00 40 9d ca 46 00 00 00 00 08 00 (ada0:ahcich0:0:0:0): CAM status: CCB request was invalid (ada0:ahcich0:0:0:0): Error 22, Unretryable error Aborting dump due to I/O error. ** DUMP FAILED (ERROR 22) ** = 0x16 db>