On Fri, Mar 18, 2016 at 04:47:26PM -0400, Neil Horman wrote:
> This BUG halt was recently reported:
>
> PID: 2879 TASK: c16adaa0 CPU: 1 COMMAND: "sctpn"
> #0 [f418dd28] crash_kexec at c04a7d8c
> #1 [f418dd7c] oops_end at c0863e02
> #2 [f418dd90] do_invalid_op at c040aaca
> #3 [f418de28] error_code (via invalid_op) at c08631a5
> EAX: f34baac0 EBX: 00000090 ECX: f418deb0 EDX: f5542950 EBP: 00000000
> DS: 007b ESI: f34ba800 ES: 007b EDI: f418dea0 GS: 00e0
> CS: 0060 EIP: c046fa5e ERR: ffffffff EFLAGS: 00010286
> #4 [f418de5c] add_timer at c046fa5e
> #5 [f418de68] sctp_do_sm at f8db8c77 [sctp]
> #6 [f418df30] sctp_primitive_SHUTDOWN at f8dcc1b5 [sctp]
> #7 [f418df48] inet_shutdown at c080baf9
> #8 [f418df5c] sys_shutdown at c079eedf
> #9 [f418df70] sys_socketcall at c079fe88
> EAX: ffffffda EBX: 0000000d ECX: bfceea90 EDX: 0937af98
> DS: 007b ESI: 0000000c ES: 007b EDI: b7150ae4
> SS: 007b ESP: bfceea7c EBP: bfceeaa8 GS: 0033
> CS: 0073 EIP: b775c424 ERR: 00000066 EFLAGS: 00000282
>
> It appears that the side effect that starts the shutdown timer was processed
> multiple times, which can happen as multiple paths can trigger it. This of
> course leads to the BUG halt in add_timer getting called.
>
> Fix seems pretty straightforward, just check before the timer is added if its
> already been started. If it has mod the timer instead to min(current
> expiration, new expiration)
>
> Its been tested but not confirmed to fix the problem, as the issue has only
> occured in production environments where test kernels are enjoined from being
> installed. It appears to be a sane fix to me though.
>
> Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
> CC: Vlad Yasevich <vyasevich@xxxxxxxxx>
> CC: "David S. Miller" <davem@xxxxxxxxxxxxx>
>
> Change notes:
>
> v2) Removed WARN_ON, as its not useful
> ---
....
> + */
> + if (WARN_ON_ONCE(timer_pending(timer))) {
Not sure what happened but it's still here :-)
> + if (time_after(timer->expires, (jiffies + timeout))) {
> + timer->expires = jiffies+timeout;
> + mod_timer(timer, timer->expires);
> + }
> + } else {
> + timer->expires = jiffies + timeout;
> + sctp_association_hold(asoc);
> + mod_timer(timer, timer->expires);
> + }
> break;
>
> case SCTP_CMD_TIMER_RESTART:
> --
> 2.5.0
>
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