e651a0b9c0
Refactor sample ring buffer ring handling to make it more robust to long running callchain collection handling r338112 introduced a (now fixed) regression that exposed a number of race conditions within the management of the sample buffers. This simplifies the handling and moves the decision to overwrite a callchain sample that has taken too long out of the NMI in to the hardlock handler. With this change the problem no longer shows up as a ring corruption but as the code spending all of its time in callchain collection. - Makes the producer / consumer index incrementing monotonic, making it easier (for me at least) to reason about. - Moves the decision to overwrite a sample from NMI context to interrupt context where we can enforce serialization. - Puts a time limit on waiting to collect a user callchain - putting a bound on head-of-line blocking causing samples to be dropped - Removes the flush routine which was previously needed to purge dangling references to the pmc from the sample buffers but now is only a source of a race condition on unload. Previously one could lock up or crash HEAD by running: pmcstat -S inst_retired.any_p -T and then hitting ^C After this change it is no longer possible. PR: 231793 Reviewed by: markj@ Approved by: re (gjb@) Differential Revision: https://reviews.freebsd.org/D17011 |
||
|---|---|---|
| .. | ||
| hwpmc_amd.c | ||
| hwpmc_amd.h | ||
| hwpmc_arm64_md.c | ||
| hwpmc_arm64.c | ||
| hwpmc_arm64.h | ||
| hwpmc_arm.c | ||
| hwpmc_armv7.c | ||
| hwpmc_armv7.h | ||
| hwpmc_core.c | ||
| hwpmc_core.h | ||
| hwpmc_e500.c | ||
| hwpmc_intel.c | ||
| hwpmc_logging.c | ||
| hwpmc_mips24k.c | ||
| hwpmc_mips74k.c | ||
| hwpmc_mips.c | ||
| hwpmc_mod.c | ||
| hwpmc_mpc7xxx.c | ||
| hwpmc_octeon.c | ||
| hwpmc_powerpc.c | ||
| hwpmc_powerpc.h | ||
| hwpmc_ppc970.c | ||
| hwpmc_riscv.h | ||
| hwpmc_soft.c | ||
| hwpmc_soft.h | ||
| hwpmc_sparc64.c | ||
| hwpmc_tsc.c | ||
| hwpmc_tsc.h | ||
| hwpmc_uncore.c | ||
| hwpmc_uncore.h | ||
| hwpmc_x86.c | ||
| hwpmc_xscale.h | ||
| pmc_events.h | ||