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The first is a fix for the way the ring buffer stores timestamps. After a restructure of the code was done, the ring buffer timestamp logic missed the fact that the first event on a sub buffer is to have a zero delta, as the full timestamp is stored on the sub buffer itself. But because the delta was not cleared to zero, the timestamp for that event will be calculated as the real timestamp + the delta from the last timestamp. This can skew the timestamps of the events and have them say they happened when they didn't really happen. That's bad. The second fix is for modifying the function graph caller site. When the stop machine was removed from updating the function tracing code, it missed updating the function graph call site location. It is still modified as if it is being done via stop machine. But it's not. This can lead to a GPF and kernel crash if the function graph call site happens to lie between cache lines and one CPU is executing it while another CPU is doing the update. It would be a very hard condition to hit, but the result is sever enough to have it fixed ASAP. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.15 (GNU/Linux) iQEcBAABAgAGBQJS/2leAAoJEKQekfcNnQGu7nYH/AltUO19AgM2sFLOLM7Q0dp4 Lg7vE8CLKtFq0fjtv/ri//fJ56Lr+/WNHiiD06aIrgnMVBbWynS0m0RO+9bhFl8/ rELiUpXTTruqljmlT2T5lPxk+ZKgtLbxK8hNywU99eLgkTwyaOwrSUol30E8pw41 UwtKg4OAn1LbjQ8/sddVynGlFDNRdqFiGTIDvhHqI6F6/QlaEX81EeZbLThDU4D/ l86fMuIdw5pb+efa29Rr0s7O4Xol7SJgnSMVgd0OYADRFmp4sg+MKxuJAUjPsHk7 9vvbylOb4w5H6lo5h7kUee3w7kG+FjYVoEx+Sqq9936+KlwtN0kbiNvl0DkrXnY= =kUmM -----END PGP SIGNATURE----- Merge tag 'trace-fixes-v3.14-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull twi tracing fixes from Steven Rostedt: "Two urgent fixes in the tracing utility. The first is a fix for the way the ring buffer stores timestamps. After a restructure of the code was done, the ring buffer timestamp logic missed the fact that the first event on a sub buffer is to have a zero delta, as the full timestamp is stored on the sub buffer itself. But because the delta was not cleared to zero, the timestamp for that event will be calculated as the real timestamp + the delta from the last timestamp. This can skew the timestamps of the events and have them say they happened when they didn't really happen. That's bad. The second fix is for modifying the function graph caller site. When the stop machine was removed from updating the function tracing code, it missed updating the function graph call site location. It is still modified as if it is being done via stop machine. But it's not. This can lead to a GPF and kernel crash if the function graph call site happens to lie between cache lines and one CPU is executing it while another CPU is doing the update. It would be a very hard condition to hit, but the result is severe enough to have it fixed ASAP" * tag 'trace-fixes-v3.14-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: ftrace/x86: Use breakpoints for converting function graph caller ring-buffer: Fix first commit on sub-buffer having non-zero delta |
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