On 2/06/21 1:30 pm, Leo Yan wrote:
Since the 64-bit atomicity is not promised in 32-bit perf, directly report the error and bail out for this case.
Now only applies on x86_64 and Arm64 platforms.
Suggested-by: Adrian Hunter adrian.hunter@intel.com
Maybe we can do better for the compat case.
We can assume the upper 32-bits change very seldom, and always increase. So for the 'read' case:
u64 first, second, last; u64 mask = (u64)((u32)-1) << 32;
do { first = READ_ONCE(pc->aux_head); rmb(); second = READ_ONCE(pc->aux_head); rmb(); last = READ_ONCE(pc->aux_head); } while ((first & mask) != (last & mask)); return second;
For the write case, we can cause a fatal error only if the new tail has non-zero upper 32-bits. That gives up to 4GiB of data before aborting:
if (tail & mask) return -1; smp_mb(); WRITE_ONCE(pc->aux_tail, tail);
Signed-off-by: Leo Yan leo.yan@linaro.org
tools/perf/builtin-record.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 3337b5f93336..f47e298281f7 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -74,6 +74,7 @@ #include <linux/zalloc.h> #include <linux/bitmap.h> #include <sys/time.h> +#include <sys/utsname.h> struct switch_output { bool enabled; @@ -848,6 +849,22 @@ static int record__mmap_evlist(struct record *rec, opts->auxtrace_sample_mode; char msg[512]; +#ifndef __LP64__
- struct utsname uts;
- int ret;
- ret = uname(&uts);
- if (ret < 0)
return ret;- if (!strncmp(uts.machine, "x86_64", 6) || !strncmp(uts.machine, "aarch64", 7) ||
!strncmp(uts.machine, "arm64", 5)) {pr_err("Error, 32-bit perf cannot record from a 64-bit kernel.\n""Please use a 64-bit version of perf instead.\n");return -ENOTSUP;- }
+#endif
- if (opts->affinity != PERF_AFFINITY_SYS) cpu__setup_cpunode_map();