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| author | Vineet Gupta <vgupta@synopsys.com> | 2015-07-14 19:50:18 +0530 |
|---|---|---|
| committer | Vineet Gupta <vgupta@synopsys.com> | 2015-08-04 09:26:34 +0530 |
| commit | e78fdfef84be13a5c2b8276e12203cdf24778596 (patch) | |
| tree | e16fad7f1d73a651d2f02deefd8f20f5bf9a018e /arch/arc/kernel/setup.c | |
| parent | 69cbe630f54ec02efe47fdb9e257e617161da370 (diff) | |
| download | linux-e78fdfef84be13a5c2b8276e12203cdf24778596.tar.bz2 | |
ARCv2: spinlock/rwlock/atomics: Delayed retry of failed SCOND with exponential backoff
This is to workaround the llock/scond livelock
HS38x4 could get into a LLOCK/SCOND livelock in case of multiple overlapping
coherency transactions in the SCU. The exclusive line state keeps rotating
among contenting cores leading to a never ending cycle. So break the cycle
by deferring the retry of failed exclusive access (SCOND). The actual delay
needed is function of number of contending cores as well as the unrelated
coherency traffic from other cores. To keep the code simple, start off with
small delay of 1 which would suffice most cases and in case of contention
double the delay. Eventually the delay is sufficient such that the coherency
pipeline is drained, thus a subsequent exclusive access would succeed.
Link: http://lkml.kernel.org/r/1438612568-28265-1-git-send-email-vgupta@synopsys.com
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc/kernel/setup.c')
| -rw-r--r-- | arch/arc/kernel/setup.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c index f2f771bd3ede..cabde9dc0696 100644 --- a/arch/arc/kernel/setup.c +++ b/arch/arc/kernel/setup.c @@ -336,6 +336,10 @@ static void arc_chk_core_config(void) pr_warn("CONFIG_ARC_FPU_SAVE_RESTORE needed for working apps\n"); else if (!cpu->extn.fpu_dp && fpu_enabled) panic("FPU non-existent, disable CONFIG_ARC_FPU_SAVE_RESTORE\n"); + + if (is_isa_arcv2() && IS_ENABLED(CONFIG_SMP) && cpu->isa.atomic && + !IS_ENABLED(CONFIG_ARC_STAR_9000923308)) + panic("llock/scond livelock workaround missing\n"); } /* |