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1bf623ebd5
The bstr exit kfuncs format the message into a shared static buffer under a raw spinlock before initiating the exit. The lock can't be taken from NMI and needlessly serializes all bstr exits system-wide. Now that exit claiming is lock-free, reverse the order: claim the exit first and format directly into the exit_info message buffer which the claim winner owns exclusively. The new scx_exit_bstr() implements the sequence, replacing scx_bstr_format(), and the shared buffer and lock are deleted; the formatter itself is what bpf_trace_printk() already runs from NMI. scx_prog_sched() callers were relying on the lock for RCU protection, which is now provided explicitly. A malformed format no longer changes or fails the requested operation: scx_bpf_exit_bstr() keeps its graceful exit kind and scx_bpf_sub_kill_bstr() still kills the child, with a fallback message carrying the formatting errno, while the sched that supplied the bad format is aborted for its bug. Before this and the previous patch, an "any" category kfunc called from NMI context could trigger scx_error() and deadlock - e.g. a tracing prog attached to a function running in NMI calling scx_bpf_dsq_peek() on a non-existent DSQ would try to grab scx_sched_lock, which may be held by the interrupted CPU. This and the previous patch fix the deadlock: scx_error() and the bstr exit kfuncs, and thus scx_bpf_error() and scx_bpf_exit(), are now safe to call from any context including NMI. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Andrea Righi <arighi@nvidia.com> |
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| .. | ||
| ext | ||
| autogroup.c | ||
| autogroup.h | ||
| build_policy.c | ||
| build_utility.c | ||
| clock.c | ||
| completion.c | ||
| core_sched.c | ||
| core.c | ||
| cpuacct.c | ||
| cpudeadline.c | ||
| cpudeadline.h | ||
| cpufreq_schedutil.c | ||
| cpufreq.c | ||
| cpupri.c | ||
| cpupri.h | ||
| cputime.c | ||
| deadline.c | ||
| debug.c | ||
| fair.c | ||
| features.h | ||
| idle.c | ||
| isolation.c | ||
| loadavg.c | ||
| Makefile | ||
| membarrier.c | ||
| pelt.c | ||
| pelt.h | ||
| psi.c | ||
| rq-offsets.c | ||
| rt.c | ||
| sched-pelt.h | ||
| sched.h | ||
| smp.h | ||
| stats.c | ||
| stats.h | ||
| stop_task.c | ||
| swait.c | ||
| syscalls.c | ||
| topology.c | ||
| wait_bit.c | ||
| wait.c | ||