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locking/csd_lock: Provide an indication of ongoing CSD-lock stall

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If a CSD-lock stall goes on long enough, it will cause an RCU CPU
stall warning.  This additional warning provides much additional
console-log traffic and little additional information.  Therefore,
provide a new csd_lock_is_stuck() function that returns true if there
is an ongoing CSD-lock stall.  This function will be used by the RCU
CPU stall warnings to provide a one-line indication of the stall when
this function returns true.

[ neeraj.upadhyay: Apply Rik van Riel feedback. ]
[ neeraj.upadhyay: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Leonardo Bras <leobras@redhat.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This commit is contained in:
Paul E. McKenney 2024-07-01 13:33:58 -07:00 committed by Neeraj Upadhyay
parent c1972c8dc9
commit ac9d45544c
3 changed files with 23 additions and 0 deletions
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6
include/linux/smp.h
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@ -294,4 +294,10 @@ int smpcfd_prepare_cpu(unsigned int cpu);
int smpcfd_dead_cpu(unsigned int cpu);
int smpcfd_dying_cpu(unsigned int cpu);
#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
bool csd_lock_is_stuck(void);
#else
static inline bool csd_lock_is_stuck(void) { return false; }
#endif
#endif /* __LINUX_SMP_H */

16
kernel/smp.c
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@ -208,6 +208,19 @@ static int csd_lock_wait_getcpu(call_single_data_t *csd)
return -1;
}
static atomic_t n_csd_lock_stuck;
/**
* csd_lock_is_stuck - Has a CSD-lock acquisition been stuck too long?
*
* Returns @true if a CSD-lock acquisition is stuck and has been stuck
* long enough for a "non-responsive CSD lock" message to be printed.
*/
bool csd_lock_is_stuck(void)
{
return !!atomic_read(&n_csd_lock_stuck);
}
/*
* Complain if too much time spent waiting. Note that only
* the CSD_TYPE_SYNC/ASYNC types provide the destination CPU,
@ -229,6 +242,7 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in
cpu = csd_lock_wait_getcpu(csd);
pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n",
*bug_id, raw_smp_processor_id(), cpu);
atomic_dec(&n_csd_lock_stuck);
return true;
}
@ -252,6 +266,8 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in
pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %lld ns for CPU#%02d %pS(%ps).\n",
firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), (s64)ts_delta,
cpu, csd->func, csd->info);
if (firsttime)
atomic_inc(&n_csd_lock_stuck);
/*
* If the CSD lock is still stuck after 5 minutes, it is unlikely
* to become unstuck. Use a signed comparison to avoid triggering

1
lib/Kconfig.debug
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@ -1614,6 +1614,7 @@ config SCF_TORTURE_TEST
config CSD_LOCK_WAIT_DEBUG
bool "Debugging for csd_lock_wait(), called from smp_call_function*()"
depends on DEBUG_KERNEL
depends on SMP
depends on 64BIT
default n
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