6.6-stable review patch. If anyone has any objections, please let me know.
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From: Rik van Riel riel@surriel.com
[ Upstream commit 94b3f0b5af2c7af69e3d6e0cdd9b0ea535f22186 ]
The CSD lock seems to get stuck in 2 "modes". When it gets stuck temporarily, it usually gets released in a few seconds, and sometimes up to one or two minutes.
If the CSD lock stays stuck for more than several minutes, it never seems to get unstuck, and gradually more and more things in the system end up also getting stuck.
In the latter case, we should just give up, so the system can dump out a little more information about what went wrong, and, with panic_on_oops and a kdump kernel loaded, dump a whole bunch more information about what might have gone wrong. In addition, there is an smp.panic_on_ipistall kernel boot parameter that by default retains the old behavior, but when set enables the panic after the CSD lock has been stuck for more than the specified number of milliseconds, as in 300,000 for five minutes.
[ paulmck: Apply Imran Khan feedback. ] [ paulmck: Apply Leonardo Bras feedback. ]
Link: https://lore.kernel.org/lkml/bc7cc8b0-f587-4451-8bcd-0daae627bcc7@paulmck-la... Signed-off-by: Rik van Riel riel@surriel.com Signed-off-by: Paul E. McKenney paulmck@kernel.org Reviewed-by: Imran Khan imran.f.khan@oracle.com Reviewed-by: Leonardo Bras leobras@redhat.com Cc: Peter Zijlstra peterz@infradead.org Cc: Valentin Schneider vschneid@redhat.com Cc: Juergen Gross jgross@suse.com Cc: Jonathan Corbet corbet@lwn.net Cc: Randy Dunlap rdunlap@infradead.org Signed-off-by: Sasha Levin sashal@kernel.org --- Documentation/admin-guide/kernel-parameters.txt | 7 +++++++ kernel/smp.c | 13 ++++++++++++- 2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0a1731a0f0ef3..41644336e3587 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5858,6 +5858,13 @@ This feature may be more efficiently disabled using the csdlock_debug- kernel parameter.
+ smp.panic_on_ipistall= [KNL] + If a csd_lock_timeout extends for more than + the specified number of milliseconds, panic the + system. By default, let CSD-lock acquisition + take as long as they take. Specifying 300,000 + for this value provides a 5-minute timeout. + smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port smsc-ircc2.ircc_sir= [HW] SIR base I/O port diff --git a/kernel/smp.c b/kernel/smp.c index 8455a53465af8..695eb13a276d2 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -170,6 +170,8 @@ static DEFINE_PER_CPU(void *, cur_csd_info);
static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */ module_param(csd_lock_timeout, ulong, 0444); +static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */ +module_param(panic_on_ipistall, int, 0444);
static atomic_t csd_bug_count = ATOMIC_INIT(0);
@@ -230,6 +232,7 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 * }
ts2 = sched_clock(); + /* How long since we last checked for a stuck CSD lock.*/ ts_delta = ts2 - *ts1; if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0)) return false; @@ -243,9 +246,17 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 * else cpux = cpu; cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */ + /* How long since this CSD lock was stuck. */ + ts_delta = ts2 - ts0; pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n", - firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts2 - ts0, + firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts_delta, cpu, csd->func, csd->info); + /* + * If the CSD lock is still stuck after 5 minutes, it is unlikely + * to become unstuck. Use a signed comparison to avoid triggering + * on underflows when the TSC is out of sync between sockets. + */ + BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC)); if (cpu_cur_csd && csd != cpu_cur_csd) { pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n", *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)),